# Student Finds Largest Prime Number Ever

SPECIAL TO THE TIMES

Itâs longer than a 400-page novel and if written out it would stretch for more than a mile.

The largest known prime number is so big that Roland Clarkson, the 19-year-old Cal State Dominguez Hills student who found it after secretly running a computer program in the campus computer lab over winter vacation, would need 277 hours to say it.

Never mind what the number is--itâs 909,526 digits long. Clarkson, of Norwalk, discovered it after running a computer for 46 days part time, and last week when the number was independently confirmed the sophomore math major became the second-youngest person to discover a world record prime number--a rare Mersenne prime, no less.

âI was born with a natural curiosity about math and it just comes naturally,â said Clarkson, whose father teaches English. âAt first I wasnât excited âcause I thought it was too good to be true, but it is, so Iâm really excited.â

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A prime number is one that is divisible only by itself and 1. An infinite number of primes exist but no one has ever come up with a formula for generating them.

Mersenne primes are rarer forms of prime numbers and Clarksonâs figure is only the 37th known Mersenne prime. Named after Marin Mersenne, a 17th century French monk and mathematician, Mersenne primes take the form of the number 2 raised to a prime power minus 1. The Mersenne formula is one of the most commonly used aids in finding new prime numbers.

Clarkson got involved in the large prime number search through his participation in GIMPS--the Great Internet Mersenne Prime Search, an Internet research project founded by a Florida computer engineer in which 4,200 number theory enthusiasts search for new Mersenne primes.

As part of the project, each participant is given a range of numbers to test and the free computer software needed for the task. The participants are all volunteers and receive no money.

Clarkson knew that finding a large prime number would take hundreds of hours, so unbeknown to anyone at the university he set up a computer in the lab at the Carson campus to run continuously during Christmas break. The Prime 95 software ran six hours a day, six days a week and when the vacation was over, Clarkson was the first at the lab to retrieve the results. He ran the last two days of the program at home.

Gordon Spence, a 38-year-old computer engineer from Hampshire, Britain, who found the previous highest prime number last August, took 15 full days to complete his calculations and prove that his number, which had 895,932 digits, was a Mersenne prime.

Keith Devlin, dean of science at St. Maryâs College of California in Moraga, in the San Francisco Bay Area, said finding the worldâs largest Mersenne number means nothing mathematically speaking, but it shows the kind of answers that society is capable of finding with improved technology.

âInstead of using one single computer, thousands of people are working together on hundreds of computers that have become one big super-computer,â Devlin said. âThis shows us the power of the World Wide Web as a computing agency and what is possible when people on computers everywhere collaborate.â

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After Clarksonâs discovery, GIMPS has decided to offer a prize to the person who finds the 38th Mersenne prime. The award: \$1 for every 1,000 digits.

Clarkson said he hopes to be the one who finds it.

âInstead of collecting . . . bottle caps I collect prime numbers,â Clarkson said. âTheyâre just as rare.â