Resolution criteria

For the purposes of this prediction, a Mersenne number is a number 2^p-1 where p is prime; these are the numbers tracked by the Great Internet Mersenne Prime Search (GIMPS). As of August 2026, the most recent Mersenne probable-prime cofactor is that of 2^17981-1, found on January 4, 2026. This market resolves to YES if, in 2026 (UTC), the cofactor of another composite Mersenne number is verified by GIMPS standards to be probably prime, regardless of when the factors of that number were found, and regardless of if or when the cofactor is proven prime. Specifically, the date of the probable-prime test that identifies a cofactor as probably prime, and the date of any certification necessary, must be December 31, 2026 or earlier on either mersenne.org or mersenne.ca.