According to a Reuters article, researchers at International Business Machines Corp. (IBM) have developed an advanced computer which has found the prime factors of the number 15. IBM claims that these factors are the numbers 3 and 5. No other computer this advanced has been built, so no one else can check IBM's work.
As noted in the article, "Previously the largest computer IBM had built was based on five atoms."
(I wonder if I should put the word "joke" at the top of entries that are intended to be funny. Experience has shown that my attempts at deadpan humor are often taken seriously.)