Description: Prime numbers are numbers that are only divisible by themselves and 1. Learn more about their properties, and see some examples. Created by Sal Khan. In this video, I want to talk a little bit about what it means to be a prime number. But as you progress through your mathematical careers, you'll see that there's actually fairly sophisticated concepts that can be built on top of the idea of a prime number. And maybe some of the encryption that your computer uses right now could be based on prime numbers.*Teacher Advisor is 100% free.