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Calculating a record prime.

As participants in the Great Internet Mersenne Prime Search (GIMPS), more than 4,000 people worldwide are chasing after the record for the largest known prime number. On Jan. 27, Roland H. Clarkson of Norwalk, Calif., hit the jackpot when his personal computer established that the 909,526-digit number [2.sup.3,021,377] - 1 is evenly divisible only by itself and 1. A sophomore at California State University Dominguez Hills, Clarkson had tested only eight exponents out of a huge number of possibilities before identifying the record prime.

Clarkson's number is the 37th known Mersenne prime. Expressed in the form [2.sup.p] - 1, where the exponent p is itself a prime, Mersenne numbers have characteristics that make it relatively easy to determine whether a candidate is prime. For example, written out in binary form, a Mersenne number consists of an unbroken string of 1s-3,021,377 of them in the case of the record prime number. That prime is surprisingly close to the previous record holder, which has the exponent 2,976,221 (SN: 9/13/97, p. 164). "I never would have imagined two Mersenne primes would be so close together," Clarkson says.

He discovered the champion prime using software written by George Woltman, a computer programmer in Orlando, Fla., who started the GIMPS project in 1996. Clarkson also relied on networking software developed by Scott Kurowski of San Jose, Calif., to coordinate the efforts of a large number of GIMPS volunteers. Kurowski's PrimeNet computer distributes work to and gathers results from thousands of copies of Woltman's program residing on computers throughout the world. By handling massive amounts of data processing over the Internet, the system represents "the world's foremost example of a new kind of computing service," Kurowski says.

To attract additional prime hunters, he has offered a cash prize of at least $1,000 for the PrimeNet discoverer of the 38th Mersenne prime. The announcement is at http://entropia. com/services.
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Title Annotation:Roland H. Clarkson achieves record for the largest known prime number in the Great Internet Mersenne Prime Search
Author:Peterson, Ivars
Publication:Science News
Article Type:Brief Article
Date:Feb 21, 1998
Words:326
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