# Largest Prime Number Ever Found Is 22 Million Digits Long

The number is only one of only 49 known "Mersenne primes" and surpasses the previous record by 5 million.

Mathematicians have unveiled a new record-breaking prime number: 2 74,207,281 – 1. It’s now the highest prime number ever discovered, eclipsing the previous record by 5 million.

The prime’s discoverer, who also found the previous record-holder, has received a $3,000 prize.

Here’s Jacob Aron, reporting for New Scientist:

This mathematical monster was discovered by Curtis Cooper at the University of Central Missouri in Warrensburg as part of the Great Internet Mersenne Prime Search (GIMPS), a collaborative effort to find new primes by pooling computing power online. It has 22,338,618 digits in total.

The GIMPS software automatically crunches through numbers, testing whether they are prime—that is, only divisible by themselves and one. Cooper’s computer actually found the prime on 17 September 2015, but a bug meant the software failed to send an email alert reporting the discovery, meaning it went unnoticed until some routine maintenance a few months later.

The pursuit of sky-high primes may seem trivial, but to mathematicians and engineers, it’s the foundation of a key piece of digital infrastructure. Public key cryptography depends on prime numbers that are exceedingly large; data can be secured by multiplying two big prime numbers together, resulting in an even bigger number that serves as a “public key.” The public key then becomes virtually impossible to decode without knowing at least one of the original prime numbers. The more primes at our disposal, the more protected we are from hackers.

Quantum computers, which can factor large numbers with breathtaking speed, threaten public key encryption—making auxiliary measures like quantum key distribution increasingly necessary. Still, the continued discovery of large prime numbers could aid security efforts and advance our understanding of the mathematical universe .

Photo credit: Isaiah van Hunen / Flickr (CC BY-SA 2.0)