January 7, 2016 — GIMPS celebrated its 20th anniversary with the discovery of the largest known prime number, 2^{74,207,281}-1. Curtis Cooper, one of many thousands of GIMPS volunteers, used one of his university’s computers to make the find. The prime number, also known as M74207281, is calculated by multiplying together 74,207,281 twos then subtracting one. It has 22,338,618 digits — almost 5 million digits longer than the previous record prime number.

Visit the Mersenne Primes page at http://www.mersenne.org/ for details.

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