10958
New Numberphile with Matt Parker about the number 10,958 comes in two parts...
Part Two, The Possible "Parker Squarey" Solution - I quite like like it, actually!
There is also some extra footage on Concatenation.
If you are wondering about references to The Parker Square, there is this video which COINCIDENTALLY was uploaded exactly one year ago.
And this video featuring concatenation is also referenced in the videos.