The largest number in the world is the googolplexian. This number starts with a 1 and has a googolplex of 0's after it.
When someone sees the number, they generally see the shorter version of the number 1 and then 10 to the 100th power. In mathematics, this number is not specially significant in any way. Someone may use it when they are trying to compare something to a very large amount, such as hypothetical chess game moves or how many subatomic particles exist. Other names for this huge number include ten thousand sexdecillion, ten duotrigintillion and ten sexdecilliard.