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At the top of the heap sit the algorithmists, who've got the most street cred among math aficionados.

Below them, you'll find the computer programmers and the professors, the engineers and the retirees, and the generally number-literate. But for more than a decade, they've each suited up for an around-the-clock bit of “recreational math” – the Great Internet Mersenne Prime Search.

It's a broad, Web-based number hunt run by a global group of math geeks, who've all downloaded software on their computers that quietly and efficiently searches for massive, “undiscovered” numbers. There are about 100,000 computers running on the system, PrimeNet, combining for 30 trillion calculations per second.

It may not be sexy, but it's fruitful. Last week, the hunters announced they'd bagged a big one: a prime number 12.9-million digits long, the largest ever proven. And it was the ragtag group of anonymous math hobbyists who, number by number, inched toward the academic achievement.

“There's a very tight-knit crowd of the few experts, and these are the algorithm folks,” explains San Diego-based Scott Kurowski, who developed the PrimeNet server. “Then there's the very significant larger crowd of people who are just enthusiasts.”

The algorithmists set up the software and guide the Web process, Mr. Kurowski said, like division commanders of sorts. Then, the enthusiasts chip in where they can, even if it means simply downloading the software on an underused work computer.

“The idea is you take a very difficult problem to solve, you break it up into smaller pieces, and hand it out to people around the world,” explains Jeff Gilchrist, a 32-year-old Canadian whose duty it was to verify the prime number discovery.

It's that distributive computing, not the find itself, that catches the eyes of math professors. “The actual number isn't as exciting as the process that went into finding it,” said Kevin Hare, assistant professor of pure mathematics at the University of Waterloo, calling the find an “incredible achievement.”

“Being on the moon isn't as impressive as getting there.”

While perhaps not math experts, the hobbyists who chip in know prime from perfect. Mr. Gilchrist is completing his PhD in systems and computer engineering at Carleton University, looking at how to crunch patient data to spot outbreaks at an Ottawa-area children's hospital. Add to that two young boys of his own, aged one and three, and he's got plenty keeping him busy. The prime number stuff, as with thousands of his PrimeNet colleagues, is pure sport – their slogan is “Serious research. Totally for fun.”

“It's more like shaving a second off a world record,” Mr. Gilchrist said. “It's sort of nice to have bragging rights, that your achievements are larger than anyone else's.”

The new number is little more than that. Prime numbers are useful “building blocks” to many equations, but using existing algorithms to find new, large primes won't likely affect ongoing research, said Cameron Stewart, a University of Waterloo professor and the Canada Research Chair in Number Theory. There are some practical implications (computer and security encryptions are based on prime numbers), but the find is more sport.

“They're a good tool. They're also mysterious; they're subtle objects …” Prof. Stewart said of prime numbers.

It was Edson Smith, a computer resource manager at the University of California Los Angeles, who found the number on Aug. 23, but he had to keep his mouth shut until Mr. Gilchrist confirmed it. He didn't have a problem with the gag order. “It's pretty easy not to tell someone a 12.9 million digit number,” he said. “Plus, they don't know what I'm talking about, anyway.”

So, the celebrations from last week's find will be confined to the math set.

“Maybe some day it can be used for something that can be used for something else, but for now it's just pure knowledge,” Mr. Smith said. “People do it because they like it.”