It actually is the reason for my online pseudonym PP44 !

The reason is it pleases the way I think about many mathematical manipulation. It is difficult to really explain why. But among the many reason :

In my mind, numbers that complement each other to form a rounder one like 2 and 8, 25 and 75, are kind of like puzzle pieces that fit together. And among those, the 4 and 6 pair clicks very nicely. The best pair that add up to 10 to me. This is definitively the main reason, and if I had to chose a second one, it would either be 44 or 6 for the same reason.

it is the first non prime integer.

It is the first (kinda non trivial) square. And the square of two that “define” parity.

The reason is it pleases the way I think about many mathematical manipulation. It is difficult to really explain why. But among the many reason :

2+2=4

2x2=4

2

^{2}=4Isn’t 1 the first non-prime integer?

1 is not a prime number