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Crypto Num Mum, Hmm

   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 
   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