Free audio book offer: http://www.audible.com/numberphile Dr James Grime delves into the largely unresolved world of Lychrel Numbers? More links & stuff in full description below ↓↓↓ James Grime: https://twitter.com/jamesgrime For audio books by Numberphile stars, go to Audible and search these names; Hannah Fry, Alex Bellos, Simon Singh, Edward Frenkel --- http://www.audible.com/numberphile Receive a Brady-signed postcard from this video: http://www.bradyharanblog.com/postcard/89 Cheryl's Birthday: https://www.youtube.com/watch?v=emiMj8cCL5E Support us on Patreon: http://www.patreon.com/numberphile NUMBERPHILE Website: http://www.numberphile.com/ Numberphile on Facebook: http://www.facebook.com/numberphile Numberphile tweets: https://twitter.com/numberphile Subscribe: http://bit.ly/Numberphile_Sub Numberphile is supported by the Mathematical Sciences Research Institute (MSRI): http://bit.ly/MSRINumberphile Videos by Brady Haran Brady's videos subreddit: http://www.reddit.com/r/BradyHaran/ Brady's latest videos across all channels: http://www.bradyharanblog.com/ Sign up for (occasional) emails: http://eepurl.com/YdjL9 Numberphile T-Shirts: null Other merchandise: https://store.dftba.com/collections/numberphile