Quick: what's the larest prime number that you know? Well, computer science professor Curtis Cooper (that's him on the left) of the University of Central Missouri in Warrensburg has just found one that has 17,425,170 digits.
All he had to do was run 1,000 computers non-stop for 39 days:
On January 25th at 23:30:26 UTC, the largest known prime number, 257,885,161-1, was discovered on Great Internet Mersenne Prime Search (GIMPS) volunteer Curtis Cooper's computer. The new prime number, 2 multiplied by itself 57,885,161 times, less one, has 17,425,170 digits. With 360,000 CPUs peaking at 150 trillion calculations per second, 17th-year GIMPS is the longest continuously-running global "grassroots supercomputing" project in Internet history.