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Claude reportedly used to factor RSA-896 challenge number

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A post published on September 19, 2026 at saweis.net says the author factored RSA-896, one of the numbers from the RSA Factoring Challenge, using Claude. RSA-896 is a modulus, the product of two large prime numbers with no publicly known factors, built and released so people can test methods of breaking it. The post states the factoring was done with Claude, gives that date, and provides the modulus along with the two prime factors it claims to have found, each roughly 135 digits long against the modulus's 270 digits.

Multiplying the two published prime factors together reproduces the published modulus exactly, so the three numbers in the post are internally consistent with each other. That consistency confirms the arithmetic of what was published; it does not by itself establish how the factors were found. The post gives no account of the method used, the hardware involved, or how long the work took.

The text does not name an author, an institution, or any collaborators: it refers only to "I" and "Claude" throughout. The Hacker News submission is posted under the account "madars," but that is the person who submitted the link, not necessarily the author of the material, and the post itself does not identify who wrote it. No conclusion about what the factorization would mean for RSA's security is drawn in the text.

Key facts

  • A post at saweis.net claims RSA-896, a public RSA Factoring Challenge number, was factored using Claude on September 19, 2026.
  • The post publishes the full 270-digit modulus alongside two claimed prime factors, p and q, each about 135 digits long.
  • Multiplying the published p and q reproduces the published modulus exactly.
  • The post gives no description of the factoring method, the hardware used, or how long the work took.
  • No author name, institution or collaborators appear in the text, which refers only to "I" and "Claude"

Why it matters

RSA-896 is one of the numbers from the RSA Factoring Challenge, published precisely so anyone can test factoring methods against it: a modulus with no publicly known factors, built by multiplying two large primes together. A credible claim to have found those factors, tied to a widely used AI model, would be notable because factoring numbers of this size is the assumption RSA encryption rests on. The post is a single, first-person account with no stated method, so it reads as a claim to check rather than a settled result.

Who it affects

The immediate audience is anyone tracking what large language models can do on hard mathematical problems, plus anyone following the state of the RSA Factoring Challenge. The post names no product, service or company, so there is no direct customer or user base beyond that shared interest.

How to use it

There is nothing to install or buy: the post is a write-up with three numbers attached, the modulus and the two claimed prime factors. Those numbers are given in full in the post, so multiplying the two stated factors and comparing the result to the stated modulus is something anyone can redo without any specialized tool.

How solid is it

The three numbers in the post are internally consistent: multiplying the two stated prime factors reproduces the stated modulus exactly. That check confirms the arithmetic of what was published, not how it was obtained. The post does not name the author, an institution, or any collaborators, gives no description of the factoring method or hardware, and does not state how long the work took, so there is no way from the text alone to judge how the factors were found.

Risks and caveats

The post offers no independent confirmation, no method and no timing, which leaves open whether the factorization was produced the way the post implies. Numbers of this size have historically required distributed, specialized computation rather than a single write-up's worth of description, so the claim would benefit from replication or a fuller account before it is treated as established.

“RSA-896 is a RSA challenge number I factored with Claude on September 19, 2026.”

— the post's author