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<!--IMPORTANT: Please do not try to write out a googolplex in standard form in the article.-->
A '''googolplex''' is the large number '''10{{sup|[[Googol|googol]]}}''', or equivalently, '''10{{sup|10{{sup|100}}}}''' or '''{{not a typo|10<sup>10,000,000,000,&ZeroWidthSpace;000,000,000,&ZeroWidthSpace;000,000,000,&ZeroWidthSpace;000,000,000,&ZeroWidthSpace;000,000,000,&ZeroWidthSpace;000,000,000,&ZeroWidthSpace;000,000,000,&ZeroWidthSpace;000,000,000,&ZeroWidthSpace;000,000,000,&ZeroWidthSpace;000,000,000,&ZeroWidthSpace;000,000,000</sup>}}'''. Written out in ordinary decimal notation, it is 1 followed by 10<sup>100</sup> zeroes; that is, a 1 followed by a [[Googol|googol]] of zeroes. Its prime factorization is 2{{sup|googol}}&nbsp;×5{{sup|googol}}.

==History==   
In 1920, [[Biography:Edward Kasner|Edward Kasner]]'s nine-year-old nephew, Milton Sirotta, coined the term ''[[Googol|googol]]'', which is 10{{sup|100}}, and then proposed the further term ''googolplex'' to be "one, followed by writing zeroes until you get tired".<ref>{{cite journal  | title = There Could Be No Google Without Edward Kasner  | first = Carl  | last = Bialik  | journal = The Wall Street Journal Online  | date = 14 June 2004  | url = https://www.wsj.com/articles/SB108575924921724042  | url-status = live  | archive-url = https://web.archive.org/web/20161130145858/http://www.wsj.com/articles/SB108575924921724042  | archive-date = 30 November 2016 }} (retrieved 17 March 2015)</ref> Kasner decided to adopt a more formal definition because "different people get tired at different times and it would never do to have Carnera [be] a better mathematician than [[Biography:Albert Einstein|Dr. Einstein]], simply because he had more endurance and could write for longer".<ref>Edward Kasner & James R. Newman (1940) Mathematics and the Imagination, page 23, NY: Simon & Schuster</ref> It thus became standardized to 10<sup>(10<sup>100</sup>)</sup> = 10<sup>10<sup>100</sup></sup>, due to the right-associativity of [[Exponentiation|exponentiation]].<ref>{{cite book |title=Compiler Construction Using Java, JavaCC, and Yacc |author1=Anthony J. Dos Reis |edition= |publisher=John Wiley & Sons |year=2012 |isbn=978-1-118-11277-9 |page=91 |url=https://books.google.com/books?id=FFcTpMi3aKQC}} [https://books.google.com/books?id=FFcTpMi3aKQC&pg=PA91 Extract of page 91]</ref>

==Size==
A typical book can be printed with 10{{sup|6}} zeros (around 400 pages with 50 lines per page and 50 zeros per line). Therefore, it requires 10{{sup|94}} such books to print all the zeros of a googolplex (that is, printing a googol zeros). If each book had a mass of 100 grams, all of them would have a total mass of 10{{sup|93}} kilograms. In comparison, [[Astronomy:Earth|Earth]]'s mass is 5.972 × 10{{sup|24}} kilograms, the mass of the [[Astronomy:Milky Way|Milky Way]] galaxy is estimated at 2.5 × 10{{sup|42}} kilograms, and the total mass of all the stars in the [[Astronomy:Observable universe|observable universe]] is estimated at 2 × 10<sup>52</sup> kg.<ref>{{cite book |title=Particle and Astroparticle Physics: Problems and Solutions |author1=Alessandro Domenico De Angelis |author2=Mário João Martins Pimenta |author3=Ruben Conceição |edition= |publisher=Springer Nature |year=2021 |isbn=978-3-030-73116-8 |page=10 |url=https://books.google.com/books?id=WXwwEAAAQBAJ}} [https://books.google.com/books?id=WXwwEAAAQBAJ&pg=PA10 Extract of page 10]</ref>

To put this in perspective, the mass of all such books required to write out a googolplex would be vastly greater than the masses of the Milky Way and the Andromeda galaxies combined (by a factor of roughly 2.0 × 10{{sup|50}}), and greater than the mass of the observable universe by a factor of roughly 7 × 10<sup>39</sup>.

=== In pure mathematics ===
In [[Pure mathematics|pure mathematics]], there are several notational methods for representing [[Large numbers|large numbers]] by which the [[Magnitude (mathematics)|magnitude]] of a googolplex could be represented, such as [[Tetration|tetration]], [[Hyperoperation|hyperoperation]], [[Knuth's up-arrow notation]], [[Steinhaus–Moser notation]], or [[Conway chained arrow notation]].

===In the physical universe===
In the PBS science program ''Cosmos: A Personal Voyage'', Episode 9: "The Lives of the Stars", [[Astronomy:Astronomer|astronomer]] and television personality [[Biography:Carl Sagan|Carl Sagan]] estimated that writing a googolplex in full decimal form (i.e., "10,000,000,000...") would be physically impossible, since doing so would require more space than is available in the known universe. Sagan gave an example that if the entire volume of the [[Astronomy:Observable universe|observable universe]] is filled with fine [[Astronomy:Cosmic dust|dust particles]] roughly 1.5 micrometers in size (0.0015 millimeters), then the number of different combinations in which the particles could be arranged and numbered would be about one googolplex.<ref>[https://www.livescience.com/31981-googol.html "Googol, Googolplex - & Google" - LiveScience.com] {{Webarchive|url=https://web.archive.org/web/20200726041136/https://www.livescience.com/31981-googol.html |date=26 July 2020 }} 8 August 2020.</ref><ref>[https://www.space.com/41721-big-numbers-universe-photos/2.html "Large Numbers That Define the Universe" - Space.com] {{Webarchive|url=https://web.archive.org/web/20191102034608/https://www.space.com/41721-big-numbers-universe-photos/2.html |date=2 November 2019 }} 8 August 2020.</ref>

Writing the number would ultimately hasten the [[Astronomy:Heat death of the universe|heat death of the universe]]: if a person can write two digits per second, then writing a googolplex would take about 1.58{{e|92}} years, which is about 1.1{{e|82}} times the accepted [[Astronomy:Age of the universe|age of the universe]], and each digit written would result in an increase of [[Physics:Entropy|entropy]] by the [[Physics:Second law of thermodynamics|second law of thermodynamics]].<ref name="fpx.de">[http://www.fpx.de/fp/Fun/Googolplex/GetAGoogol.html Page, Don, "How to Get a Googolplex"] {{webarchive|url=https://web.archive.org/web/20061106072349/http://www.fpx.de/fp/Fun/Googolplex/GetAGoogol.html |date=6 November 2006 }}, 3 June 2001.</ref> {{failed verification|date=April 2023}}

{{10^|97}} is a high estimate of the elementary particles existing in the visible universe (not including [[Astronomy:Dark matter|dark matter]]), mostly photons and other massless force carriers.<ref>{{cite web
 |author=Robert Munafo
 |date=24 July 2013
 |title=Notable Properties of Specific Numbers
 |url=http://mrob.com/pub/math/numbers-19.html
 |access-date=2013-08-28
 |archive-date=6 October 2020
 |archive-url=https://web.archive.org/web/20201006200300/http://mrob.com/pub/math/numbers-19.html
 |url-status=live
 }}</ref>

==Mod ''n''==
The [[Modular arithmetic|residues (mod ''n'')]] of a googolplex, starting with mod 1, are:
:0, 0, 1, 0, 0, 4, 4, 0, 1, 0, 1, 4, 3, 4, 10, 0, 1, 10, 9, 0, 4, 12, 13, 16, 0, 16, 10, 4, 24, 10, 5, 0, 1, 18, 25, 28, 10, 28, 16, 0, 1, 4, 24, 12, 10, 36, 9, 16, 4, 0, ... {{OEIS|id=A067007}}
This sequence is the same as the sequence of [[Googol#Properties|residues (mod ''n'') of a googol]] up until the 17th position.

== See also ==
* [[Graham's number]]
* [[Names of large numbers]]
* [[Orders of magnitude (numbers)]]
* [[Skewes's number]]

==References==
{{Reflist}}

==External links==
{{Commons}}
* {{MathWorld | urlname=Googolplex | title=Googolplex}}
* {{PlanetMath | urlname=Googolplex | title=googolplex}}
* {{cite web|title=Googol and Googolplex|url=http://www.numberphile.com/videos/googolplex.html|work=Numberphile|publisher=[[Biography:Brady Haran|Brady Haran]]|author=Padilla, Tony|author2=Symonds, Ria|access-date=6 April 2013|archive-url=https://web.archive.org/web/20140329024608/http://www.numberphile.com/videos/googolplex.html|archive-date=29 March 2014|url-status=dead}}

{{Large numbers}}

[[Category:Integers]]
[[Category:Large integers]]
[[Category:Units of amount]]
[[Category:Numbers]]

{{Sourceattribution|Googolplex}}