Largest known prime number discovered

Not every number plugged into this calculation produces a prime number, however, computers have been able to use the simple formula to search for even longer prime numbers. Founded in 1996, GIMPS is the longest running “grassroots supercomputing” project in Internet history and is responsible for the discovery of all 15 of the largest known Mersenne primes. It’s officially written as 2-1 should you want to impress someone who knows about numbers, like a tax inspector or a bank manager.

A computer at the University of Central Missouri has discovered the world’s longest prime number – and it’s 22 million characters long.

Generally, these volunteers are looking for prime numbers because they are the “key” to certain kinds of cryptography – referred to as public-key encryption.

Why search for such numbers? They are also used to encrypt private messages. However, the program the team used to discover it is interesting because it’s reliance on shared internet computing technically makes it one of the most powerful computational systems on the planet.

If you’re so inclined, you can download a .zip file of the number here.

Mersenne primes are named following a French monk who examined them.

While there are infinitely many prime numbers, it can be somewhat tricky to determine whether an arbitrary huge number (huge in this case meaning a number with millions of digits and being so unfathomably large it’s hard if not impossible to actually visualize how large it is) is actually prime. Scott Kurowski and Aaron Blosser of GIMPS also share credit for the discovery. So far are known according to Gimps 49 of them, you will find a complete list here.

One way to find primes is take the number 2 and factor it with another number, then subtract one and finally check if it meets conditions for being prime. The search for the highest known prime is a long-established mathematical quest, of interest now more as a test of computing power rather than for any practical use of the number itself.

Once it was noticed, the discovery was verified independently by other people with different software and hardware, and announced on January 7, when GIMPS celebrated its 20th anniversary.