Will a second Mersenne probable-prime cofactor be found in 2026?
Not enough price history for this range yet.
Source: ProbCast snapshots (Manifold)
This market has resolved. The final Manifold price was 64.0%.
- Final market price
- 64.0%
- Event deadline
- December 31, 2026 at 6:59 PM ET
- Probability 24 hours before event deadline
- 64.0%
- Probability seven days before event deadline
- 64.0%
- Venue status
- resolved
ProbCast Reliability Summary
Will a second Mersenne probable-prime cofactor be found in 2026? The final Manifold price was 64.0%. This market has resolved. The final Manifold price was 64.0%.
- Market data as of
- September 11, 2026 at 6:53 AM ET
- ProbCast assessment generated
- October 21, 2026 at 4:39 AM ET
- Source
- Manifold
- Event deadline
- December 31, 2026 at 6:59 PM ET
- Market status
- Resolved
- Data updated
- 40d ago
What this market actually measures
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 summary shows the opening of the venue's official rules. ProbCast has not yet generated an independent plain-English interpretation for this contract — review the full rules before relying on it.
View full official resolution rules
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.