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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