Missouri mathematician discovers largest known prime number — and it is 22 million digits long

Dr. Curtis Cooper of the University of Central Missouri has discovered the largest known prime number, at 22 million digits long. It is an entire 5 million digits longer than the previous largest prime.

Prime numbers are numbers that are only divisible by themselves and one, such as two, three, five, and seven. Their discovery is particularly important in the world of computer encryption, where they are used to secure online banking, shopping, and private messaging, BBC reports. However, current encryption is typically hundreds of digits long, not millions; Cooper's discovery is currently too large to be of use.

It is still an exciting find: The Great Internet Mersenne Prime Search, or GIMPS, has found 15 of the largest prime numbers in the past 20 years, and says there could be an infinite number to discover. Mainly primes are found using computers, but they are said to be "discovered" when a person notices and reports it.

The Week

Escape your echo chamber. Get the facts behind the news, plus analysis from multiple perspectives.

SUBSCRIBE & SAVE

Sign up for The Week's Free Newsletters

From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.

From our morning news briefing to a weekly Good News Newsletter, get the best of The Week delivered directly to your inbox.

Sign up

So, what exactly is the number? The world's largest known prime is written 2^74,207,281-1 — in other words, multiply two by itself 74,207,281 times, then subtract one.

Go ahead, do the math.