31 is one of the special Mersenne Prime numbers. They are related to perfect numbers. More links & stuff in full description below ↓↓↓ See our perfect number video at https://www.youtube.com/watch?v=ZfKTD5lvToE This video features Dr James Grime. All our presenters are featured at http://www.numberphile.com/team/index.html 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 Videos by Brady Haran Patreon: http://www.patreon.com/numberphile 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