Today, people use complex computing networks to search for prime numbers with millions of digits. But early mathematicians were running these calculations by hand.

Prime numbers are absolutely essential to modern computer security -- and, possibly, to communicating with alien life forms. Here's how they work.

The online computer game “Is this prime?” tests a player’s knowledge of prime numbers—and just surpassed 2,999,999 attempts. Give it a whirl.

For example, 7 is a prime number since I'm left with a remainder or a fractional component if I divide 7 by anything other than itself or 1. 6 is not a prime because I can divide 6 by 2 and get 3.

A basic feature of number theory, prime numbers are also a fundamental building block of computer science, from hashtables to cryptography.

The world's largest prime number clocks in at nearly 13 million digits. It's a type of number called a Mersenne, and mathematicians are using the Internet to outsource the computing power to find ...