The Great Internet Mersenne Prime Search, more commonly referred to as GIMPS (not to be mistaken with the image editing software), has announced the discovery of the largest known prime number. That number is a huge 2^77,232,917-1, which contains 23,249,425 digits. To more easily refer to it, the number is also being called M77232917. Dozens of hours have gone into verifying the number.
Mersenne announced the project earlier this week, explaining that the discovery was made via a computer volunteered to the project by Jonathan Pace. How do you get to the prime number? By multiply twos (the number 2) together a total of 77,232,917 times, then subtracting 1.
That makes for a massive number, one that has almost a million more digits than the now-second place prime number record. According to GIMPS, the newly discovered prime number is part of an “extremely rare” special class called Mersenne primes. M77232917 is the fiftieth Mersenne prime discovered thus far, and the next one — whenever it is found — will be even harder to discover.
What did it take to discover this latest Mersenne prime? According to GIMPS, the primality proof required half a dozen endless days of computing; the number crunching was performed with an Intel i5-6600. Once that was finished, the prime then had to be verified, which required four different individuals using various programs and hardware to compute it.
The verification took, individually speaking, 37, 34, 73, and 82 hours. Pace, the engineer who discovered it, has been hunting for a big prime number for more than 14 years, according to GIMPS; he is eligible to get $3,000 as an award for his work.