A **googol** is the number 10^{100}, that is, the digit 1 followed by one hundred zeroes. The term was coined in 1938 by nine-year-old Milton Sirotta, nephew of American mathematician Edward Kasner. Kasner announced the concept in his book *Mathematics and the Imagination*.

A googol is "approximately" equal to the factorial of 70, and its prime factors are only 2 and 5. In binary it would take up 333 bits.

The googol has few practical uses as of yet, and is most often invoked in mathematics teaching. Kasner created it to illustrate the difference between an unimaginably large number and infinity.

A googol can be written in conventional notation, as follows:

- 1 googol = 10
^{100}= 10, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000, 000

A googol is greater than the number of atoms in the known universe. Since this is also the number of zeroes in a googolplex, it would not be possible to write down or store this number (googolplex) in decimal notation, even if all the matter in the known universe were converted into paper and ink or disk drives.

The Internet search engine, Google, was named as a play on the number googol.

*Googol* was the answer to the million-pound question on *Who Wants to Be a Millionaire* when Major Charles Ingram attempted to defraud the quiz show on 10 September 2001. (For details, see the *Who Wants to Be a Millionaire* entry.)

See also: googolgon, googolhedron, duotrigintillion

- Kasner, Edward & Newman, James Roy
*Mathematics and the Imagination*(New York, NY, USA: Simon and Schuster, 1967; Dover Pubns, April 2001; London: Penguin, 1940, ISBN 0486417034).