Something special about 399 (and 2015) - Numberphile

It is the lowest Lucas-Carmichael Number... Featuring Ed Copeland. More links & stuff in full description below ↓↓↓ More about Ed's real work: http://bit.ly/CopelandGoesLong With thanks to these Patreon supporters: Herschal Sanders (from Susan) Today I Found Out Lê OK Merli Alex Bozzi Thomas J Petersen Spiked Math Filipe Junqueira Bill Shillito plusunim Micky Baeza Tracy Parry Andrzej 'Yester' Fiedukowicz Stan Ciprian Rich Pantano (from Jill) Joshua Wilson & Andrew Touchet Kelly N Cooper Stimson 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: https://teespring.com/stores/numberphile Other merchandise: https://store.dftba.com/collections/numberphile