The World's Largest Prime Number has 22 Million Digits
It may not be practical (yet), but it's pretty nifty.

A computer at the University of Central Missouri has calculated the world's largest prime number, coming in at 22,338,618 digits and surpassing the previous record by nearly 5 million digits. Prime numbers are an important component in computer encryption, though this one is "too large to currently be of practical value," according to the Great Internet Mersenne Prime Search, a group dedicated to discovering rare prime numbers. The new number is called "M74207281."

Dr. Curtis Cooper, a professor at UCM, volunteered the computer that found today's new No. 1, and he happens to be a previous prime-number record-holder. M74207281 is a Mersenne Prime, a class of rare primes found by multiplying two with itself for a while, and then subtracting one (2P-1). Today's number is 274,207,281-1, for example. This is only the 49th Mersenne Prime discovered so far.

Cooper is eligible for a $3,000 research discovery award from GIMPS. Next up, the organization and its volunteers hope to discover a 100 million-digit prime number, which could net them $150,000 from the Electronic Frontier Foundation.

Stand-up mathematician Matt Parker (pictured above) breaks down Mersenne Primes and the new record in the below video.