The geek walks among us, part 2

The Associated Press reported on December 11 that the largest prime number found so far turned up on the computer or a 26-year old Michigan State University graduate student named Michael Shafer.

A prime number is one that is evenly divisible only by itself and one. There are eight such numbers below 20: 2, 3, 5, 7, 11, 13, 17, and 19. (One itself, being part of the definition, it usually not considered to be a prime.) As numbers get larger, primes get rarer because any multiple of a smaller number can't be a prime (because it's evenly divisible by that smaller number).

The newest prime has 6,320,430 digits. If you allow 80 characters per line and 56 lines per page, it would take over 1400 pages just to write the number out.

The number is actually what's known as a Mersenne prime, a special subcategory of primes important in the branch of mathematics known as number theory.

Perhaps more important is the way the number was discovered. Shafer was one of over 200,000 people who let a piece of software work on the problem in the background while they did other things with their computers. By sharing information via a central website (a task also handled by the software), those numerous home and office computers produced results equivalent to - even better than - an advanced supercomputer.

This linking of computers has been used for other purposes but this is another demonstration of its potential to solve problems and do calculations beyond the most powerful single units.

For more on the search for Mersenne primes, check out http://www.mersenne.org//20996011.htm.