Largest known Prime number written out

50th known Mersenne prime ever found, on computer volunteered in collaborative project

A collaborative computer project has discovered the largest known prime number. The new prime number is nearly one million digits larger than the previous record prime number, in a special class of extremely rare prime numbers known as Mersenne primes.

The Great Internet Mersenne Prime Search (GIMPS) has discovered the largest known prime number, 2^77,232,917-1, having 23,249,425 digits. A computer volunteered by Jonathan Pace made the find on December 26, 2017. Jonathan is one of thousands of volunteers using free GIMPS software.

The new prime number, also known as M77232917, is calculated by multiplying together 77,232,917 twos, and then subtracting one. It is nearly one million digits larger than the previous record prime number, in a special class of extremely rare prime numbers known as Mersenne primes. It is only the 50th known Mersenne prime ever discovered, each increasingly difficult to find. Mersenne primes were named for the French monk Marin Mersenne, who studied these numbers more than 350 years ago. GIMPS, founded in 1996, has discovered the last 16 Mersenne primes. Volunteers download a free program to search for these primes, with a cash award offered to anyone lucky enough to find a new prime. Prof. Chris Caldwell maintains an authoritative web site on the largest known primes, and has an excellent history of Mersenne primes.