[tarvaina]

Stray thought: Why 4 and 9? Because the joke is funniest if the number is completely ordinary.

0 and 1 are special and so are all prime numbers. 6 is out because it's the maximum die throw. And one figure is more ordinary than two figures, or negatives, or decimals. That leaves 4 and 9.

[grahamlee]

That makes 4 and 9 the only two uninteresting numbers, which is interesting, so they’re out too!

Douglas Adams said the same about 42. It’s the answer because it’s completely banal.

[_pigpen__]

Everyone knows that six is the most boring number. https://youtu.be/G4OTRRmyTAA?feature=shared

[Velorivox]

How come prime numbers are special but squares aren’t? 4 and 9 both being squares seems to be a more striking commonality than your logic here…

[tarvaina]

Yeah. Alternative explanation: I'd say 3 and 7 are out because they often come up in fairy takes etc as magical. 5 is out because it's half of ten and the number of fingers. 2 is out because it is too small.

[darkerside]

The perfect squares are the most ordinary?

[dreghgh]

What about 8?

[bee_rider]

Maximum throw for a battle axe in 5e d&d, of course.

I dunno actually. Maybe because 4*2=8? The two picks have the property of not being related really.

[tim333]

8, 16, 32, 64 pop up a lot in computer circles.

[tarvaina]

Oh, right! I forgot about it. I guess 8 would do too.