A 270-Digit Number Has Been Factored, and the Public Record Moves Again
Stephen A. Weis has published the two prime factors of RSA-896, a 270-digit number from the RSA Factoring Challenge that nobody had broken in public before. He dates the factorization to Sept. 19, 2026.
That moves the public record for the largest RSA challenge number ever factored to 896 bits, from 862 bits. Wikipedia's list of RSA numbers records both results and dates the 862-bit factorization to Sept. 3, 2026, 16 days earlier.
The challenge numbers exist to measure this. RSA Laboratories published them to track the practical difficulty of factoring large integers, the same entry says. What moved is that measure, not the safety of the RSA keys in everyday use, which are longer. Every larger challenge number on the list is still unfactored.
Weis writes on his site that he factored the number with Claude, Anthropic's AI model. The page names no hardware, no algorithm and no figure for how long the computation ran.
The result does not rest on his account. Both published factors are prime, and multiplying them returns the published number exactly, which anyone holding the digits can check. Weis posted the number and both factors in full.
The challenge itself is long closed. RSA Laboratories ended it in 2007 and the remaining prizes were withdrawn, the same entry records, so the numbers still standing are factored for the record alone.
