On 18 February Martin Nowak, an eye surgeon and amateur mathematician from Germany, found the largest prime number yet, with an amazing 7 816 230 digits. He used more than 50 days of CPU time on a 2.4 GHz Pentium 4 computer - plus some additional help. Tens of thousands of participants in the Great Internet Mersenne Prime Search (GIMPS) lent spare cycles to the effort, demonstrating how a computational Grid can do big calculations.
The result was independently verified in five days by Tony Reix of Grenoble, using a 16 Itanium CPU Bull NovaScale 5000 HPC and again by Jeff Gilchrist of Elytra Enterprises in Ottawa, who used 15 days of time on 12 CPUs of a Compaq Alpha GS160 1.2 GHz CPU server at SHARCNET. The prime is a "Mersenne Prime", which is of the form 2p-1, where p is a prime. In this case the power is 25 964 951.
There is no immediate application of such an enormous prime, but for those who like a challenge the Electronic Frontier Foundation is offering a prize of $100,000 for the first prime with 10 million digits and $250,000 for a prime with 1000 million digits. You can also obtain a poster containing the entire new prime number!