Skewes' Massive Number
Dr James Grime on the epic Skewes' Number.
Lynda free trial (worth a look): http://www.lynda.com/numberphile
Prime numbers: http://bit.ly/primevids
Graham's Number: http://bit.ly/GrahamsNumber
A small bit we chopped from this video: https://youtu.be/qgN6DnZmEvg