Monday, June 5

What's so special about 13532385396179?

Thanks to James Davis — who stands to collect $1000 for finding a counterexample to a John H. Conway conjecture (problem 5):

13532385396179 = 13 * 53^2 * 3853 * 96179

Very nice! I'm glad it ended up this way. When I wrote my Climb to a prime piece on 12 October 2014, I was under the distinct impression that it would have been enough to evolve the number 20 to a prime in order to claim the prize. I now see that Bill Cheswick's "Five $1000 Problems" pdf was last updated 13 October 2014 — one day later — and I no longer read it that way.


  1. Hey Hans.
    Similar to the comment by James Davis, you're the only person I can talk to about one of John H. Conway's conjectures (problem 3, the Thrackle Problem). I believe I have two counter-examples to this problem and so, similar to James Davis's comment, contact me at

    1. Lots of people have worked on the thrackles.