New Biggest Prime Number = 2 to the 74 Mil … Uh, It’s Big

Photo credit: Tucker Nichols

By Kenneth Chang

The largest known prime number, newly discovered, is almost five million digits longer than the previous record-holder.

In a computer laboratory at a satellite campus of the University of Central Missouri, an otherwise nondescript desktop computer, machine No. 5 in Room 143, multiplied 74,207,281 twos together and subtracted 1. It then checked that this number was not divisible by any positive integer except 1 and itself — the definition of a prime number.

This immense number can only be practically written down in mathematical notation using exponents: 274,207,281 − 1.

The previous largest was 257,885,161 − 1, which has a mere 17 million or so digits.

This is the 15th prime number found by the Great Internet Mersenne Prime Search, or Gimps, for short, a volunteer project that has been running for 20 years. “I’ve always been interested in prime numbers,” said George Woltman, who founded Gimps after he had retired. “I had a lot of time on my hands,” he said.

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