Graham's number is an unimaginably large number that arose in the field of combinatorics (a branch of mathematics dealing with counting and arrangement). For a long time, it held the Guinness World Record for the largest number ever used in a serious mathematical proof. ​To give you an idea of its scale: it is so large that the observable universe doesn't contain enough space to write down its digits, even if every digit were the size of an atom. In fact, if you tried to hold all the digits of G

Mastering Combinatorics: Understanding Factorials in Math

Graham's Number Explained: The Immensity and Math Behind It