With Shor's algorithm (the thing that would make this headline about "Quantum computers will break the encryption that protects the Internet" true) AFAIK the answer is that quantum computers have found 21 = 7 x 3
Because of interest in using quantum computers to factor big numbers there's a reason to do something other than Shor's algorithm with a big machine that can't run Shor's algorithm and thus get a big impressive number. This approach has factored six or seven digit numbers. Which your PC could also trivially do, and it doesn't use Shor's algorithm either.
