Largest prime number yet discovered has 22 million digits

New year. New largest prime.

A computer in Missouri has discovered the largest known prime number, 2^74,207,281– 1. It is about 22 million digits long, 5 million digits longer than the previous largest known prime, which was discovered in January 2013.

Prime numbers are numbers that are divisible only by themselves and one, such as 2, 3, 5, 7, 11 and 13. 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. It’s a fun challenge too.

Primes that can be written as one less than a power of two, i.e 2ⁿ – 1 for some n, are known as Mersenne primes after the French monk Marin Mersenne who investigated their properties 350 years ago. They are the easiest large primes to find since they provide numbers to aim for, and there’s a quick way to test they are prime.

The new record-breaking prime was discovered by the Great Internet Mersenne Prime Search, a project that links thousands of computers around the world to look for prime numbers. It is both the longest continuously running distributed computing project as well as the one with most unfortunate acronym, Gimps. Since it started 20 years ago, Gimps has discovered the 15 largest Mersenne primes.

Curtis Cooper, of the University of Central Missouri, was running Gimps on several of the university’s computers. One of these computers found the new highest prime last September but it went unnoticed until discovered a few months later by routine maintenance.

It is the fourth time Dr Cooper has found a new largest prime – the 2013 number was also his. He is eligible for a $3000 Gimps research award. The next major goal is to win the $150,000 award administered by the Electronic Frontier Foundation offered for finding the first 100 million digit prime number.

The quest for highest prime will go on for ever since there an infinite number of them.