What Comes After Untrigintillion?

There's quadrillion, quintillion, sextillion, septillion, octillion, nonillion, decillion and more. Each is a thousand of the previous one. There's even a humongous number called vigintillion, a one with 63 zeros.

What is 1,000,000,000,000,000 called?

Trillion is a 1 with 12 zeros after it, and it looks like this: 1,000,000,000,000. The next named number after trillion is quadrillion, which is a 1 with 15 zeros after it: 1,000,000,000,000,000.

What is the largest named number?

According to many books (such as Mathematics, A human Endeavor by Harold Jacobs)2 the googol is one of the largest numbers ever named. The googolplex is 1 followed by a googol zeros. More recently, Skewer's number is the largest number ever used in a mathematical proof.