Piphilology
Part of a series of articles on the 
mathematical constant π 

3.1415926535897932384626433... 
Uses 
Properties 
Value 
People 
History 
In culture 
Related topics 
Piphilology comprises the creation and use of mnemonic techniques to remember many digits of the mathematical constant π. The word is a play on the word "pi" itself and of the linguistic field of philology.
There are many ways to memorize π, including the use of piems (a portmanteau, formed by combining pi and poem), which are poems that represent π in a way such that the length of each word (in letters) represents a digit. Here is an example of a piem: "Now I need a drink, alcoholic of course, after the heavy lectures involving quantum mechanics." Notice how the first word has three letters, the second word has one, the third has four, the fourth has one, the fifth has five, and so on. In longer examples, 10letter words are used to represent the digit zero, and this rule is extended to handle repeated digits in socalled Pilish writing. The short story "Cadaeic Cadenza" records the first 3,834 digits of π in this manner, and a 10,000word novel, Not A Wake, has been written accordingly.
However, poems prove to be inefficient for large memorizations of π. Other methods include remembering patterns in the numbers (for instance, the year 1971 appears in the first fifty digits of π) and the method of loci (which has been used to memorize π to 67,890 digits).
History
Until the 20th century, the number of digits of pi which mathematicians had the stamina to calculate by hand remained in the hundreds, so that memorization of all known digits at the time was possible. In 1949 a computer was used to calculate π to 2,000 places, presenting one of the earliest opportunities for a more difficult challenge.
Later computers calculated pi to extraordinary numbers of digits (2.7 trillion as of August 2010), and people began memorizing more and more of the output. The world record for the number of digits memorized has exploded since the mid1990s, and it stood at 100,000 as of October 2006. The previous record (83,431) was set by the same person (Akira Haraguchi) on July 2, 2005, and the record previous to that (42,195) was held by Hiroyuki Goto. An institution from Germany provides the details of the "Pi World Ranking".
Examples in English
The most common mnemonic technique is to memorize a socalled "piem" (a wordplay on "pi" and "poem") in which the number of letters in each word is equal to the corresponding digit of π. This famous example for 15 digits has several variations, including:
 How I want a drink, alcoholic of course, after the heavy chapters involving quantum mechanics!  Sir James Hopwood Jeans
Short mnemonics such as these, of course, do not take one very far down π's infinite road. Instead, they are intended more as amusing doggerel. If even less accuracy suffices, the following examples can be used:
 How I wish I could recollect pi easily today!
 May I have a large container of coffee, cream and sugar?
This second one gives the value of π as 3.1415926535, while the first only brings it to the second five. Indeed, many published poems use truncation instead of one of the several roundings,^{[citation needed]} thereby producing a lessaccurate result when the first omitted digit is greater than or equal to five. It is advantageous to use truncation in memorizing if the individual intends to study more places later on, otherwise one will be remembering erroneous digits.
Another mnemonic is:
 The point I said a blind Bulgarian in France could see
In this mnemonic the word "point" represents the decimal point itself.
Yet another example is:
 How I wish I could recollect, of circle round, the exact relation Arkimedes (or Archimede) unwound.
In this example, the spelling of Archimedes is normalised to nine. Although 'Archimedes' is, today, a more correct spelling of the ancient Greek mathematician's name in English, Archimede is also often seen when this mnemonic is given, since Archimède is the more correct spelling in some languages, such as French. This mnemonic also contains a rounding error because the digit represented by the last word "Arkimedes" (9) in 3.141592653589 is followed by 7 in π, which would cause the last two digits to round up.
Longer mnemonics employ the same concept. This example created by Peter M. Brigham incorporates twenty decimal digits:
 How I wish I could enumerate pi easily, since all these bullshit mnemonics prevent recalling any of pi's sequence more simply.
Poems
Some mnemonics, such as this poem which gives the three and the first 20 decimal digits, use the separation of the poem's title and main body to represent the decimal point:
 Pie
 I wish I could determine pi
 Eureka, cried the great inventor
 Christmas pudding, Christmas pie
 Is the problem's very center.
Another, more poetic version is:
 Sir, I have a rhyme excelling,
 In mystic power and magic spelling,
 Celestial spirits elucidate,
 For my own problems can't relate.
Extensions to 30 or 31 decimals of the same proceed as follows:


There are minor variations on the above rhyme, which still allow pi to be worked out correctly. However, one variation replaces the word "lexicon's" with "lesson's" and in doing so, incorrectly indicates that the 18th digit is seven.
The logologist Dmitri Borgmann gives the following 30word poem in his book, Language on Vacation: An Olio of Orthographical Oddities:
 Now, a moon, a lover refulgent in flight,
 Sails the black silence's loneliest ellipse.
 Computers use pi, the constant, when polite,
 Or gentle data for sad tracking aid at eclipse.
In the fantasy book, Somewhen by David Saul, a 35word piem both provides a description of the constant pi and the digits. The text is also laid out as a circle to provide another clue to the readers as to the purpose of the poem. In this example, the word "nothing" is used to represent the digit zero.
 It's a fact
 A ratio immutable
 Of circle round and width,
 Produces geometry's deepest conundrum.
 For as the numerals stay random,
 No repeat lets out its presence,
 Yet it forever stretches forth.
 Nothing to eternity.
The following sonnet is a mnemonic for pi to 75 decimal places in iambic pentameter:
 Now I defy a tenet gallantly
 Of circle canon law: these integers
 Importing circles' quotients are, we see,
 Unwieldy long series of cockle burs
 Put all together, get no clarity;
 Mnemonics shan't describeth so reformed
 Creating, with a grammercy plainly,
 A sonnet liberated yet conformed.
 Strangely, the queer'st rules I manipulate
 Being followéd, do facilitate
 Whimsical musings from geometric bard.
 This poesy, unabashed as it's distressed,
 Evolvéd coherent  a simple test,
 Discov'ring poetry no numerals jarred.
Note that in this example, 10letter words are used to represent the digit zero.
Other poems use sound as a mnemonic technique, as in the following poem which rhymes with the first 140 decimal places of pi using a blend of assonance, slant rhyme, and perfect rhyme:
 dreams number us like pi. runes shift. nights rewind
 daytime pleasurepiles. dreamlooms create our id.
 moods shift. words deviate. needs brew. pleasures rise.
 time slows. too late? wait! foreign minds live in
 us! quickminds, freeminds, mindswenevermind,
 unknown, gyrate! neurorhymes measure our
 minds, for our minds rhyme. crude egoemanations
 distort nodes. id, (whose basic neurospacetime rhymes),
 plays its tune. space drones before fate unites
 dreams’ lore to unsung measures. whole dimensions
 gyrate. new numbergames donate quick minds &
 weave through fate’s loom. fears, hopes, digits, or devils
 collide here—labor stored in goldmines, lives, lightcone
 piles. fate loops through dreams & pleasurelooms….
Note that "dreams number us like pi" corresponds to "314159," and so on. Soundbased mnemonic techniques, unlike pilish, do not require that the letters in each word be counted in order to recall the digits of pi. However, where soundbased mnemonics use assonance, extra care must be taken to distinguish "nine" and "five," which contain the same vowel sound. In this example, the author assumes the convention that zero is often called "O."
Piku
The piku follows the rules of conventional haiku (three lines of 5, 7 and 5 syllables), but with the added mnemonic trick that each word contains the same number of letters as the numerals of pi, e.g.
 How I love a verse
 Contrived to unhusk dryly
 One image nutshell
Songs
In 2004, Andrew Huang wrote a song that was a mnemonic for the first fifty digits of pi, titled "I am the first 50 digits of pi". The first line is:
 Man, I can’t  I shan’t!  formulate an anthem where the words comprise mnemonics, dreaded mnemonics for pi.
In 2013, Huang extended the song to include the first 100 digits of pi, and changed the title to "Pi Mnemonic Song".
Lengthier works
There are piphilologists who have written texts that encode hundreds or thousands of digits. This is an example of constrained writing, known as "Pilish". For example, Poe, E.: Near a Raven represents 740 digits, Cadaeic Cadenza encodes 3,835, and Not A Wake extends to 10,000 digits.
Soundbased mnemonics
It is also possible to use the rhythm and sound of the spoken digits themselves as a memorization device. The mathematician John Horton Conway composed the following arrangement for the first 100 digits,
_ _ _ 3 point 1415 9265 35 ^ ^ _ _ _ _ _ _ __ 8979 3238 4626 4338 3279 ** **^^ ^^ **** . _ _ __ _ _ _ . _ . 502 884 197 169 399 375 105 820 974 944 ^ ^ ^ ^ 59230 78164 _ _ _ _ 0628 6208 998 6280 ^^ ^^ ^^ .. _ .._ 34825 34211 70679, ^ ^
where the accents indicate various kinds of repetition.
Another mnemonic system used commonly in the memorization of pi is the Mnemonic major system, where single numbers are translated into basic sounds. A combination of these sounds creates a word, which can then be translated back into numbers. When combined with the Method of loci, this becomes a very powerful memorization tool.


Examples in other languages
Persian
خرد  و  دانش  و  آگاهی  دانشمندان 
Wisdom, science, and the knowledge of scholars, 
Counting the letters in each word (additionally separated by "") gives 10 decimal places of π: خرد (kherad) = 3, و (va) = 1, دانش (daanesh) = 4, و (va) = 1, آگاهی (aagaahi) = 5, ...
Hungarian
Nem a régi s durva közelítés, 
It is not the old and rough approximation, 
An interesting (not math themed) alternative:
Bíre, éreze ember nyugalmat, 
Whether has, whether feels a man a peace of mind 
Another alternative:
 Íme a szám: a görög periféria pi betűje.
 Euler meg Viète végtelen összeggel közelít értékéhez.
 Lám, őt már Egyiptom, Kína, Európa is akarta, hogy
 „ama kör kerülete úgy ki lehetne számlálva”.
Albanian
Kur i hyej, e kryej, sigurisht, po përtoj andaj nuk fitoj 
If I start dealing with it, I will do it, but I am lazy therefore I do not win. 
German
This statement yields π to twentytwo decimal places:
 Wie, o dies π macht ernstlich so vielen viele Müh. Lernt immerhin, Mägdelein, leichte Verselein, wie so zum Beispiel dies dürfte zu merken sein.
English translation that doesn't encode pi:
 How, oh this π seriously makes so many struggles to so many. Learn at least, girls, simple little verses, just such as this one should be memorizable.
Looser English translation that encodes pi:
 Woe! O this π makes seriously so muchly many's woe.
French
The following poem composed of Alexandrins consists of words each with a number of letters that yields π to 126 decimal places:
Que j’aime à faire apprendre un nombre utile aux sages ! 
How I like to teach this number useful to the wise. 
An alternative beginning:
 Que j’aime à faire apprendre un nombre utile aux sages !
 Glorieux Archimède, artiste ingénieur,
 Toi de qui Syracuse aime encore la gloire,
 Soit ton nom conservé par de savants grimoires !
 ...
Katharevousa (archaizing) Greek
Yielding π to 22 decimal places:
Ἀεὶ ὁ Θεὸς ὀ Μέγας γεωμετρεῖ, 
The Great God applies geometry forever; 
Spanish
The following piem, giving π to 31 decimal places, is well known in Argentina:
Fue y cayó. Y queda solamente la inútil cifra con pocos destinos poderosos, tristes devenires sin el más sencillo bien. Idiota, re idiota, sabe que sus encantos son ya latosos decimales. Pobre... 
It went and it fell. And only the useless figure remains, with little powerful destinies, sad future without the simplest goodness. Idiotic, very idiotic, it knows that its charms are now boring decimals. Poor... 
Another. This piem gives π (correctly rounded) to 10 decimal places. (If you prefer to not round π, then replace "cosmos" with "cielo".)
Sol y luna y mundo proclaman al eterno Autor del Cosmos. 
Sun and moon and world proclaim the eternal Author of the Cosmos. (Or "heaven", not Cosmos, if using "cielo".) 
Irish
(7 decimal places)
Níl i mata, a shaoi, eolaíocht nó feidhm. 
Wise one, mathematics has neither science nor use. 
Romanian
One of the Romanian versions of Pi poems is:
Dar o știm, e număr important ce trebuie iubit 
But we know, it's an important number which should be loved 
There is another phrase known in Romanian that will help to memorize the number by eight decimal places: Așa e bine a scrie renumitul și utilul număr. — "This is the way to write the renowned and useful number."
Another alternative for 15 decimal places:
Ion a luat o carte, biografie, în latina veche. Are cinci capitole originale clasice latinești. — "Ion has bought a book, a biography, in old latin. It has five classical original latin chapters."
Russian
In the Russian language, there is a wellknown phrase in the reform of 1917 orthography of old tradition:
Кто и шутя, и скоро пожелаетъ «Пи» узнать число — ужъ знаетъ. 
The one who would wish to know the number pi easily and quickly already knows it. 
A more modern rhyme is:
Это я знаю и помню прекрасно, 
I know the following and remember it perfectly, 
A short approximation is: "Что я знаю о кругах?" (What do I know about circles?)
In addition, there are several nonfolklore verses that simply rhyme the digits of pi "as is"; for examples, see the Russian version of this article.
Polish
The verse of Polish mathematician Witold Rybczyński (35 decimal places):
Daj, o pani, o boska Mnemozyno, pi liczbę, którą też zowią ponętnie ludolfiną, pamięci przekazać tak, by jej dowolnie oraz szybko do pomocy użyć, gdy się problemu nie da inaczej rozwiązać, pauza — to zastąpić liczbami. 
Allow, o lady, o divine Mnemosyne, the pi number, which also is called enticingly the ludolphine, to pass to memory, so as to use it freely and quickly for help, when the problem can not be otherwise resolved, pause — this replace by the numbers. 
(Note that the dash stands for zero.)
The verse of Polish mathematician Kazimierz Cwojdziński (23 decimal places):
Kuć i orać w dzień zawzięcie, bo plonów niema bez trudu. Złocisty szczęścia okręcie kołyszesz … Kuć. My nie czekajmy cudu. Robota to potęga ludu. 
Hammer and plow by day obstinately, because there are no fruits without effort. Golden ship of happiness, rocking... Hammer. Let us not wait for a miracle. Labor is the power of the people. 
(12 decimal places):
Był i jest i wieki sławionym ów będzie, który kół obwód średnicą wymierzył. 
There was, and there is, and through centuries renowned will be, who circle's circumference measured with its diameter. 
(10 decimal places)
Kto z woli i myśli zapragnie Pi spisać cyfry, ten zdoła 
Who out of will and mind shall wish to write the digits of Pi, shall succeed. 
An occasionally seen verse related to Mundial Argentina and the Polish football team (30 decimal places):
Portuguese
(11 decimal places)
Cai a neve e novas ferrovias de marfim serão por casas trocadas. 
The snow falls and new ivory railroads will be exchanged by houses. 
(8 decimal places)
Com o zero o lente reprovará os alunos. 
With zero the university professor will fail the students. 
Or in Brazilian Portuguese:
Sim, é útil e fácil memorizar um número grato aos sábios. 
Yes, it's useful and easy to memorize a number dear to the wisemen. 
A piem written in a more poetic manner:
Sou o amor, 
I am the love, 
Japanese
Japanese piphilology has countless mnemonics based on punning words with numbers. This is especially easy in Japanese because there are two or three ways to pronounce each digit, and the language has relatively few phonemes to begin with. For example, to 31 decimal places:
身 一つ 世 一つ 生 く に 無 意 味 い わ く な く 身 ふ み や 読 む 似 ろ よ さん ざん 闇 に な く 3. 1 4 1 5 9 2 6 5 3 5 8 9 7 9 3 2 3 8 4 6 2 6 4 3 3 8 3 2 7 9 mi hitotsu yo hitotsu iku ni muimi iwakunaku mi fumiya yomu niro yo san zan yami ni naku
This is close to being ungrammatical nonsense, but a loose translation prioritizing word order yields:
 A person is one; the world is one:
 to live this way, it's meaningless, one says, and cries,
 "step on it, will ya!" then reads—be the same!
 Crying uncontrollably in the dark.
Japanese children also use songs built on this principle to memorize the multiplication table.
Chinese
It is possible to construct piphilogical poems in Chinese by using homophones or nearhomophones of the numbers zero through nine, as in the following well known example which covers 22 decimal places of π. In this example the character meaning "mountain" (山 shān) is used to represent the number "three" (三 sān), the character meaning "I" (吾 wú) is used to represent the number "five" (五 wǔ), and the characters meaning "temple" (寺 sì) and "die" (死 sǐ) are used to represent the number "four" (四 sì). Some of the mnemonic characters used in this poem, for example "kill" (殺 shā) for "three" (三 sān), "jug" (壺 hú) for "five" (五 wǔ), "happiness" (樂 lè) for "six" (六 liù) and "eat" (吃 chī) for "seven" (七 qī), are not very close phonetically in Mandarin/Putonghua.
山 巔 一 寺 一 壺 酒 shān diān yī sì yī hú jiǔ 3 . 1 4 1 5 9 爾 樂 苦 煞 吾 ěr lè kǔ shā wú 2 6 5 3 5 把 酒 吃 酒 殺 爾 bǎ jiǔ chī jiǔ shā ěr 8 9 7 9 3 2 殺 不 死 樂 爾 樂 shā bù sǐ lè ěr lè 3 8 4 6 2 6
This can be translated as:
 On a mountain top a temple and a jug of wine.
 Your happiness makes me so bitter;
 Take some wine and drink, the wine will kill you;
 If it does not kill you, I will rejoice in your happiness.
Turkish
Sen, o alan o çevre bölününce ve sonsuz rakam ile çıkan değişken dizilimli sayısın. 
You are the number with infinite digits in changing order, which is found when the circumference and the area is divided. 
Czech
(nine decimal places)
Sám u sebe v hlavě magického pí číslic deset mám. 
I have ten digits of magical pi in my head. 
(12 decimal places)
Lín a kapr u hráze prohlídli si rybáře, udici měl novou, jikrnáči neuplovou. 
Tench and carp by the dam watched the fisher. He has a new rod, fish will not escape. 
(13 decimal places)
Dej, ó Bože, a číslo Ludolfovo já navždy pomnu, pro větší naplnění moudrosti početní. 
Oh God, let me to remember the pi forever, for the increase of mathematical skills. 
(30 decimal places)
Mám ó bože ó velký pamatovat si takový cifer řad, velký slovutný Archimedes, pomáhej trápenému, dej mu moc, nazpaměť nechť odříká ty slavné sice, ale tak protivné nám, ach, číslice Ludolfovy! 
Shall I, God oh almighty, remember such a long string of numbers, great and famous Archimedes, help my careworn being, give me the power, to recite by heart all the digits, which may be famous, but also hated by some of us, the digits of Ludolph van Ceulen. 
Serbian
(16 decimal places)
Čak i Grci i stari Vavilonci su kazali: obime kad deliš krugovim prečnikom dobijaš neophodan nam pi. 
Even Greeks and Old Babylonians have told: when dividing circumferences with circle's diameter you obtain the indispensable pi. 
Italian
(30 decimal places)
Non è dato a tutti ricordare il numero aureo del sommo filosofo Archimede. Certuni sostengon che si può ricordar tale numero, ma questi soli poi non recitano che un centone insensato. 
Not anybody can retain the golden number of the great philosopher Archimedes. There are who claim it is possible to recall this number, but then they just recite a senseless cento. 
(10 decimal places) Chi è nudo e crepa limonando la tubera, lieto lui crepa
Sanskrit
The Katapayadi System of verses is basically a system of code so that things can be defined in a way so that people can remember. The code is as follows:
1  2  3  4  5  6  7  8  9 

क  ख  ग  घ  ङ  च  छ  ज  झ 
ट  ठ  ड  ढ  ण  त  थ  द  ध 
प  फ  ब  भ  म  
य  र  ल  व  श  ष  स  ह  क्ष 
With the above key in place, Sri Bharathi Krishna Tirtha in his Vedic Mathematics gives the following verse:
गोपी भाग्य मधुव्रात श्रुङ्गिशो दधिसन्धिग  खलजीवित खाताव गलहालारसंधार  If we replace the code from the above table in the above verse, here is what we get. 31 41 5926 535 89793 23846 264 33832792 That gives us π/10=0.31415926535897932384626433832792
Slovene
The following piem gives π to 30 decimal places.
Naj z rimo v pesmi počastimo še nekoga: 
Now I, even I, would celebrate 
—A.C. Orr  —Translated by Janko Moder 
Memorization record holders
Even before computers calculated π, memorizing a record number of digits became an obsession for some people^{[who?]}. The record for memorizing digits of π, certified by Guinness World Records, is 70,000 digits, recited in India by Rajveer Meena in 9 hours and 27 minutes on 21 March 2015. On October 3, 2006, Akira Haraguchi, a retired Japanese engineer, claimed to have recited 100,000 decimal places, but the claim was not verified by Guinness World Records.
David Fiore was an early record holder for pi memorization. Fiore's record stood as an American record for more than 27 years, which remains the longest time period for an American recordholder. He was the first person to break the 10,000 digit mark.
Suresh Kumar Sharma holds Limca Book of Records for the most decimal places of pi recited by memory. He rattled off 70,030 numbers in 17 hours 14 minutes on October 21, 2015.
See also
Notes and references
This article lacks ISBNs for the books listed in it. by listing ISBNs. If the {{Cite book}} or {{Citation}} templates are in use, you may add ISBNs automatically, or discuss this issue on the talk page. (April 2015) 
 ^ Rosenthal, Jeffrey S. (2018). "A Note About Piems".
 ^ "Not A Wake: A Dream Embodying π's Digits Fully For 10000 Decimals". Retrieved 20110303.
 ^ Raz, A; Packard, MG; Alexander, GM; Buhle, JT; Zhu, H; Yu, S; Peterson, BS (2009). "A slice of pi : An exploratory neuroimaging study of digit encoding and retrieval in a superior memorist". Neurocase. 6 (5): 1–12. doi:10.1080/13554790902776896. PMC 4323087. PMID 19585350.
 ^ ^{a} ^{b} "Pi calculation smashes records". Retrieved 20100512.
 ^ O'Connor, J J; Robertson, E F. "A history of Pi". Retrieved 20070202.
 ^ "(broken link)". Yahoo! News (in Japanese). Retrieved 20070202.^{[dead link]}
 ^ "Japanese breaks pi memory record". BBC News. London. 20050702. Retrieved 20070202.
 ^ "Home". piworldrankinglist.com.
 ^ Hawkesworth, Alan S. (March 1931). "Two Mnemonics". The American Mathematical Monthly. 38 (3): 158. doi:10.2307/2300971. JSTOR 2300971.
The following mnemonic for π is due to Sir James Hopwood Jeans
 ^ "Mnemonics for the Number Pi". camosun.bc.ca. Archived from the original on 20160219. Retrieved 20160209.
 ^ "Mnemonics > Number mnemonics". funwithwords.com.
 ^ Borgmann, Dmitri A. (1965). Language on Vacation: An Olio of Orthographical Oddities. Charles Scribner's Sons.
 ^ Doerfel, Joel. "Sonnet 72 (Ode to Pi)". Retrieved 20120426.
 ^ "SONGS TO WEAR PANTS TO " Blog Archive " I AM THE FIRST FIFTY DIGITS OF PI". songstowearpantsto.com.
 ^ "SONGS TO WEAR PANTS TO " Lyrics". songstowearpantsto.com.
 ^ "PI MNEMONIC SONG". YouTube. 14 March 2013. Archived from the original on 20211221.
 ^ "Poe, E.: Near a Raven", cadaeic.net
 ^ "Not A Wake", cadaeic.net
 ^ "Math Forum » Discussions » History » mathhistorylist", Math Forum
 ^ http://litemind.com/majorsystem/ , Major Memory System
 ^ Browne, Malcolm W. (5 July 1988). "Mathematicians Turn to Prose in an Effort to Remember Pi". The New York Times. Retrieved 20180317.
 ^ "Poezii pentru numărul Pi" (in Romanian). Secretele lui Lovendal. 20090102. Archived from the original on 20100124. Retrieved 20121219.
 ^ "Strona Renaty Staszkiewicz". cba.pl.
 ^ (in Japanese) 暗記法 Japanese mnemonics for π (and some other languages as well)
 ^ Bhanu Murthy, T. S. (1992). A Modern Introduction to Ancient Indian Mathematics.
 ^ "Most Pi Places Memorized", Guinness World Records.
 ^ Otake, Tomoko (17 December 2006). "How can anyone remember 100,000 numbers?". The Japan Times. Retrieved 27 October 2007.
 ^ David Fiore's record is memorialized: http://www.piworldrankinglist.com/lists/details/fiore.html
 ^ "With pi in mind". DNA India. 19 March 2017.
 ^ "Failed to crack IIT, but now helps to 'shape' best minds". Times of India. 18 February 2016.
 ^ "Pi Day 2017: Meet the recordholders for memorizing digits of pi". Mic Network. 14 March 2017.
 ^ "Pi world ranking list". Pi world ranking list. 2 January 2018.