Let me show you some techniques and shortcuts that will let you easily identify whether any number under 120 is a prime number or not. Along the way, I’ll also show some symmetrical patterns within composite numbers, rectangles, and square roots!

I noticed a little problem with the version of this I uploaded a few hours ago, so I took that down and here’s the fixed version. Hope you all enjoy!

Special thanks to Evan Clark and to all of my Patreon supporters:
Max, George Carozzi, Peter Offut, Tybie Fitzhugh, Henry Spencer, Mitch Harding, YbabFlow, Joseph Rissler, Plenty W, Quinn Moyer, Julius 420, Philip Rogers, Ilmori Fajt, Brandon, August Taub, Ira Sanborn, Matthew Chudleigh, Cornelis Van Der Bent, Craig Butz, Mark S, Thorbjorn M H, Mathias Ermatinger, Edward Clarke, and Christopher Masto, Joshua S, Joost Doesberg, Adam, Chris Reisenbichler, Stan Seibert, Izeck, Beugul, OmegaRogue, Florian, William Hawkes, Michael Friemann, Claudio Fanelli, and Julian Zassenhaus.
(To join that list of people supporting this channel, and get cool bonus content, check out the Combo Class Patreon at   / comboclass  )

By the way, I've started putting shorts on this channel but they typically won't go to notifications or subscription feeds (they typically have been on my @Domotro channel and did so well for that channel that I want more people on that shorts page to find this channel too). They will be available on the "shorts" tab on this channel, and I will link the recent ones in video descriptions like this. Here are the two I've put on this channel so far:
Here's the newest one:    • Shorts  
Here's one about a geometric representation of the "difference of squares" identity:    • Shorts  
Here's one about the difference between 1/0 and 0/0:    • Shorts  

If you want to mail me anything (such as any clocks/dice/etc. that you'd like to see in the background of Grade -2), here's my private mailbox address (not my home address). If you're going to send anything, please watch this short video first:    • You Can Now Mail Me Things to Put in ...  
Domotro
1442 A Walnut Street, Box # 401
Berkeley, CA 94709

Come chat with other combo lords on the Discord server here:   / discord  
and there is a subreddit here:   / comboclass  

If you want to try to help with Combo Class in some way, or collaborate in some form, reach out at combouniversity(at)gmail(dot)com

In case people search any of these words, some topics mentioned in this video are: prime numbers, composite numbers, factors, rectangles, square numbers, square roots, symmetry, and more!

If you're reading this, you must be interested in Combo Class. Make sure to leave a comment on this video so the algorithm shows it to more people :)

DISCLAIMER: Do not copy any uses of fire, sharp items, or other dangerous tools or activities you may see in this series. These videos are for educational (and entertainment) purposes.