For those of us who need a moment or two to recall what a prime number is, then require a minute or so more to mentally check off the easy ones before hitting 29 and wondering if it is indeed only divisible by the number one and itself, to hear that someone has confirmed the existence of a prime number with 12.9 million digits is beyond comprehension. But that is exactly what Carleton PhD student Jeff Gilchrist has done. A member of Great Internet Mersenne Prime Search, the international team that discovered the number – the largest prime ever found – Mr. Gilchrist, 32, personally verified the figure over 16 days using one of Carleton’s supercomputers. The astounding find, credited to a computing manager at the University of California, qualifies for a $100,000 award from a US computer group for being the first discovered prime number with over 10 million digits. Mr. Gilchrist, as checker, will not receive any of the prize money but is happy enough to share in the glory. “It’s very exciting for me,” says the systems and computer engineering student. “In the mathematical world, this is like an Olympic event where everyone is trying to beat the last record.” In those terms, the new record makes Mr. Gilchrist a seven-time medalist. Over the years, he has helped to verify six other record-breaking primes.