What is a 21-digit number?

A 21-digit number is a number that has 21 digits where the first digit must be 1 or greater. On this page, we will answer three questions for you: What is the smallest 21-digit number? What is the largest 21-digit number? How many 21-digit numbers are there?

Smallest 21-digit number
The smallest 21-digit number is 1 followed by 20 zeros. This number is called one hundred quintillion.

Largest 21-digit number
The largest 21-digit number is 9 followed by another 20 nines. This number is called nine hundred ninety-nine quintillion nine hundred ninety-nine quadrillion nine hundred ninety-nine trillion nine hundred ninety-nine billion nine hundred ninety-nine million nine hundred ninety-nine thousand nine hundred ninety-nine.

Total number of 21-digit numbers
There are a total of nine hundred quintillion different 21-digit numbers. nine hundred quintillion is 9 followed by 20 zeros.

Digit Numbers
Here you can learn about another digit number.

What is a 22-digit number?
Go here for information about the next digit number on our list that we have information about.