For 9 years, computers at Central Missouri State University have been sifting through number after number, searching for a record-breaking prime. The effort finally paid off last month when one of the CMSU computers identified the 43rd Mersenne prime, setting the record for the largest known prime number.
This behemoth, 230402457 – 1, runs to a whopping 9,152,052 decimal digits, handily topping the previous champion, 225964951 – 1, which has 7,816,230 decimal digits. Like all primes, it’s evenly divisible only by itself and 1.