# meaning explained: Why people use the hashtag symbol

Filler Graham's number is one of the largest numbers ever used in a serious mathematical proof. It was introduced by mathematician Ronald Graham while solving a problem in an area of mathematics called Ramsey theory. To understand how unimaginably huge Graham's number is, compare it to numbers like: One million = 106 One billion = 10° The number of atoms in the observable universe = 1080 Graham's number is so much larger that even writing it in ordinary decimal form is physically impossible. The