RSA numbers
set of large semiprimes
In mathematics, the RSA numbers are a set of large semiprimes (numbers with exactly two prime factors) that were part of the RSA Factoring Challenge. The challenge was to find the prime factors of each number. It was created by RSA Laboratories in March 1991 to encourage research into computational number theory and the practical difficulty of factoring large integers. The challenge was ended in 2007.
History
RSA Laboratories (which is an initialism of the creators of the technique, Rivest, Shamir and Adleman) published a number of semiprimes with 100 to 617 decimal digits. Cash prizes of varying size, up to US$200,000 (and prizes up to $20,000 awarded), were offered for factorization of some of them. The smallest RSA number was factored in a few days. Most of the numbers have still not been factored and many of them are expected to remain unfactored for many years to come.
As of September 2026, the smallest 24 as well as the 26th of the 54 listed numbers have been factored.
While the RSA challenge officially ended in 2007, people are still attempting to find the factorizations.
“RSA numbers” enters the record as set of large semiprimes. Crown Archives preserves that source wording while asking what numbers, large and semiprimes can confirm, complicate or overturn.
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The citation trail is more important than the brevity of the summary: it shows where individual claims can be examined in context. The source revision retrieved here is dated Sep 21, 2026. The linked authority identifier is Q1072840. None of the 0 selected statements returned an explicit reference. The first chronological checks are 1991, 2007 and 2026.
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This entry incorporates text from “RSA numbers” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.