googol
Definition A googol equals to the number ${10}^{100}$, that is, a one followed by one hundred zeros. A googolplex is is ten raised to the power of a googol, i.e., ${10}^{({10}^{100})}$.
This is already a huge number. For instance, it is more than the number of atoms in the known universe^{}. A googoplex is even larger. In fact, since a googolplex has a googol number of zeros in its decimal representation, a googoplex has more digits than there are atoms in our universe. Thus, even if all matter in the universe were at disposal, it would not be possible to write down the decimal representation of a googolplex [1].
Properties

1.
A googol is approximately the factorial^{} of $70$. The only prime factors^{} in a googol and a googolplex are $2$ and $5$ [1].

2.
Using Stirling’s formula^{} we can approximate the factorial of a googol to obtain
$${10}^{100}!\approx {10}^{9.95\cdot {10}^{101}}.$$ 
3.
A googoplex plus one is not a prime. One factor is 316912650057057350374175801344000001 [5].
History and etymology
The googol was created by the American mathematician Edward Kasner (18781955) [4] in [2] to illustrate the difference^{} between an unimaginably large number and infinity^{}. The name ’googol’ was supposedly coined by Kasner’s nineyearold nephew Milton Sirotta in 1938 when asked to give a name for a huge number. The name googol was perhaps influenced by the comic strip character Barney Google [1, 3]. The name of the search engine google was inspired by the number googol [6].
References
 1 Wikipedia’s http://en2.wikipedia.org/wiki/Googolentry on googol.
 2 Kasner, Edward&Newman, James Roy,Mathematics and the Imagination, (New York, NY, U SA: Simon and Schuster, 1967; Dover Pubns, April 2001; London: Penguin, 1940, ISBN 0486417034).
 3 Douglas Harper’s http://www.etymonline.com/g3etym.htmEtymology online dictionary, Googol 12/2003.
 4 Wikipedia’s http://en2.wikipedia.org/wiki/Edward_Kasnerentry on Edward Kasner.
 5 Robert Munafo, http://www.mrob.com/pub/math/numbers21.htmlweb page on large numbers.
 6 Google corporate information: http://www.google.com/corporate/history.htmlGoogle Milestones.
Title  googol 

Canonical name  Googol 
Date of creation  20130322 12:25:31 
Last modified on  20130322 12:25:31 
Owner  Mathprof (13753) 
Last modified by  Mathprof (13753) 
Numerical id  19 
Author  Mathprof (13753) 
Entry type  Definition 
Classification  msc 1100 
Related topic  Googolplex 