The Washington Post, September 9, 1996, p. A2. Computers: Number Crunchers' 1 and Only It's big. It's beautiful. And it's prime. Computer scientists at Cray Research have discovered the largest known prime number. A prime number, for those of us who have forgotten grade school mathematics, can only be divided by itself and by 1. Smaller primes include 2, 3, 5, 7 and 11. The new one, 2^1257787-1, is a bit bigger. Printed out, the 378,632 digit number would take up 12 newspaper pages. "We're pretty confident that this is the largest known prime number," said researcher Paul Gage. There are an infinite number of primes but they are extremely difficult to find. The newly discovered prime number is of a type known a "Mersenne" prime, named for a 17th century French monk and mathematician. It is easier to prove the prime-ness of Mersenne numbers than other primes, thanks to complex mathematical software. Cray runs the prime-testing program to search for bugs in its new supercomputers. Gage said the discovery of the prime was a happy byproduct of the process. The new number was discovered during a six-hour run testing a new Cray T94 system. Prime numbers are useful in the field of cryptography, where they are used to help construct virtually unbreakable codes. The new prime is far larger than those commonly used. Said Gage, "A cryptographer interested in numbers this big wouldn't be talking about it." -- John Schwartz [End]