The largest prime number in the world has been discovered in Missouri by the Great Internet Mersenne Prime Search project, better known as GIMPS. The record breaking number — which, like all primes, can only be divided by itself and one — is a staggering 22 million digits in length. That's 5 million digits longer than the previous record-holder, which was also discovered by GIMPS back in January 2013. If you really want to know, the new biggest Prime in the world starts with a "3" and ends with a "1."
As the GIMPS project admits in its official press release, a prime number this size is actually too big to be of any practical use, but its discovery still has symbolic value, as well as testing the capacity of the software that pinned it down. Although the hardware in this case isn't exactly supercomputer level — the prime was discovered after "31 days of non-stop computing" by Dr. Curtis Cooper of the University of Central Missouri on computer kitted out with just an Intel Core i7 processor. Cooper's computer was one of a network making calculations using the same GIMPS software, but still — this isn't an activity that's as intensive as mining Bitcoin.
GIMPS are looking out for a prime with 100 million digits next
The record-breaking prime itself is what's known as a Mersenne prime — a variety which was discovered by a 16th century French monk named Marin Mersenne. These primes are calculated in the format 2n -1, which makes them comparatively easy to track down and verify, even when they're obscenely large. The 10 largest known prime numbers are all Mersenne primes and every single one was discovered by GIMPS. The new record breaker was found by multiplying two by itself 74,207,281 times, and then subtracting one. Simple.
But although the number of prime numbers in the world may be infinite, every time we find a new one, it gets trickier to find the next. The next major goal for volunteers who join the search will be to find a prime number with 100 million digits — a goal which has a $150,000 prize. To get a feeling of what sort of number you're looking for, you can download the new biggest prime in the world (all 22 million digits of it) here.