The largest known prime number, 2^{57,885,161} - 1, was discovered on January 25, 2013 after a search involving a great deal of computer time spread across many computers.

So how large is this number? Big. Really big. It has 17,425,170 digits, four times as many digits as the number that was previously the largest known prime. If you were to print this number in 12 point font, it would go on for 30 miles. If you wanted to download it in a computer file, it would take up 22.5 megabytes. You could include it in a Gmail message but just barely. It's a big number.

You probably remember that prime numbers are integers that are larger than 1 and divisible only by themselves and 1. If you wanted to create a list, it would begin 2, 3, 5, 7, 11, 13, 17, and so forth. In fact, your list would never end; over two thousand years ago, Euclid proved that there are infinitely many primes.

Our newest known prime is an example of a Mersenne prime, named after the 17th century French monk, Marin Mersenne, who made an extensive study of them. Mersenne primes are prime numbers that have the form 2^{n} - 1. If you create a list of the numbers 2^{n} - 1, it would start like this: