Numberphile is a Youtube channel and show about numbers. Most episodes are about a specific number which can be anywhere from one digit to indescribably many digits in length and discuss some feature of that number, either in mathematics or in the wider world. Aside from general schema the topics are varied, touching the Enigma Machine, Barcodes, and Yahtzee.

Having run since at least 2011 and with over two million subscribers at the time of writing this, one has to assume Numberphile is doing something right. The first is that it's produced by Brady Haran, who worked for the BBC before starting Numberphile and several other infotainment channels. As such, the pacing, camera work, cuts, and occasional info-graphics are all of professional quality. Third, the laid back, slightly conversational tone most of the mathematicians take make the videos almost relaxing. Forth, the topics are presented in such away that most adults will be able to follow along but not so simplified that you aren't actually learning the subject. All of this comes together to form a show that does a really good job of explaining complicated topics in bite sized chunks while actually still teaching something about math.

And it does actually teach things, for instance this video does a good job of explaining why there are only five Platonic Solids, this shows what e actually is, and this is an explanation of the Collatz Conjecture which is apparently really hard to prove despite being very easy to explain. All of this amounts to a really solid gateway program into mathematics which is good since TV has given up on educational programs as far as my occasional viewing of the Discovery channel, History channel, etcetera can discern. Episodes average five to ten minutes. You can find the channel here.