The Huffington Post reports:
The largest prime number has been discovered — and it's 17,425,170 digits long. The new prime number crushes the last one discovered in 2008, which was a paltry 12,978,189 digits long.

The number — 2 raised to the 57,885,161 power minus 1 — was discovered by University of Central Missouri mathematician Curtis Cooper as part of a giant network of volunteer computers devoted to finding primes, similar to projects like SETI@Home, which downloads and analyzes radio telescope data in the Search for Extraterrestrial Intelligence (SETI). The network, called the Great Internet Mersenne Prime Search (GIMPS) harnesses about 360,000 processors operating at 150 trillion calculations per second. This is the third prime number discovered by Cooper.