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How a professor found the largest known prime number

A Missouri university professor has found a new prime number as part of GIMPS, a citizen-science project that works using grassroots efforts by thousands of volunteer researchers.

Using computers hooked up to the Great Internet Mersenne Prime Search (GIMPS), Curtis Cooper at the University of Central Missouri discovered a prime number 22 million digits long last year, though it was only recently recognized

For more than a decade, students at the University of Central Missouri have been browsing the Web, checking their email, or writing their papers all without knowing that, as they worked, their lab computers were processing a massive, decades-long citizen science project.

The Great Internet Mersenne Prime Search (GIMPS) announced the discovery of the world's longest prime number, using software running in the background of student lab computers, Alyssa Navarro reported for Tech Times.

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Dr. Curtis Cooper, a number theoretician and computer science professor at the University of Central Missouri, joined the GIMPS project in 1998, one year after its launch by computer scientist George Woltman. He uses the computers to search for undiscovered prime numbers, which means a number divisible only by itself and 1. His 22-million-digit number, known for convenience as M74207281, is the 49th discovered Mersenne prime number, and the fourth he has discovered.

“A student found out about [GIMPS in 1998] and said, 'You guys are in number theory and you’re in computer science, and this kind of marries the two together, and you have access to a lot of computers,' – thinking I control all the computers," Dr. Cooper told The Christian Science Monitor with a laugh.

The discovery has brought him mathematical celebrity and prize money from the Electronic Frontiers Foundation, but this comes after two decades of patient work with both computers and people. Administrators and computer technicians at the University of Central Missouri initially had doubts about both the project's worthiness as a use of school resources and about the potential for a security breach through the software.

At that time, Cooper emailed his results directly to the founder, George Woltman.

By 2000, Cooper had gained the trust of school officials, and computer programmer Scott Kurowski developed software that could be hosted on a server and downloaded to other computers. Because Mr. Kurowski got his start with the GIMPS project, he makes it available to prime-number enthusiasts free of charge.

"That made my life easier," Cooper says. "I remember going from four computers to jumping to about 30 computers.”

In 2005 he found his first Mersenne prime number – a number to the power of two, minus one – and opposition from the school became less of a problem. The discovery was exciting, Cooper says, but its value to science is in the process. The discovery demonstrates how thousands of volunteers can conduct a long-term research project.

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"There’s so many numbers and the project is so massive that they farm it out on the grassroots level," Cooper says. "Then they pull out the heavy machinery and check it."

Running and monitoring the software takes patience. Cooper's project tests up to 60 numbers per day, and he has found only two numbers in five years of that high-intensity testing.

"It’s not really good odds, but in the end it’s really exciting when it does come up," Cooper says. "I think that’s how it is in a lot of these fields that everyone is covering – if it was easy somebody would do it already."

The four prime numbers Cooper has found are too long to currently have more than theoretical value, but he says prime numbers a few hundred digits long are now useful for everyday data encryption.

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