Largest Prime Number Should Have Been Discovered Last September

It has 22 million digits!

By now, you may have heard that a team at the University of Central Missouri has found the largest prime number ever — one with over 22 million digits! What you may not know is that the computer that they were using actually found it back in September, but failed to notify the team. A glitch in the system meant that they only discovered it during a maintenance cycle on January 7.

How did the team go about looking for an incredibly large prime number? They crunched numbers on a single, Intel-based PC. Curtis Cooper and his team are part of the Great Internet Mersenne Prime Search (GIMPS) collaboration and used software developed by GIMPS called prime95.

SEE ALSO: Pi Found in Mathematical Calculation of the Hydrogen Atom

A Mersenne prime, named after French monk Marin Mersenne who studied them over 350 years ago, is a particular type of prime number where the prime is one less than a power of two. For example:

2²-1=3

2³-1=7

2⁵-1=31

In this case, the prime number they found is 2^74,207,281-1. Only 49 Mersenne primes have been discovered so far (since not all Mersenne numbers are prime) and GIMPS is responsible for the most recent 15.

If you were to print out the whole number using a font where each digit was 1 mm wide, the whole printout would be about 22 km long, so it’s a good thing there’s an abridged way to write it!

This isn’t the first time that Cooper and his team have broken the record for the largest prime number — in fact, it’s the fourth! This prime, named M74207281, is almost 5 million digits longer than the one whose record it broke.

According to a press release, “the prime was independently verified using both different programs and different hardware.”

This find has earned them a $3000 reward, but their real goal is to earn the $150,000 offered to anyone who can find a prime number with 100 million digits.