On February 18, 2005, Dr. Martin Nowak from Germany, found the new largest known prime number, 2^25,964,951 -1. The prime number has 7,816,230 digits.
It took more than 50 days of calculations on Dr. Nowak's 2.4 GHz Pentium 4 computer. The new prime was independently verified in five days by two reserachers in France and Spain.
Read more about it, here