[oh_my_goodness]

I mean 4 is equivalent to 4 mod 21. That part's not AI slop.

[JohnKemeny]

I think, in fact, for every prime number p at least 5, 4 mod p is (congruent to) 4.

[oh_my_goodness]

Even without the restriction to primes, that feels like a pretty good guess!

[freehorse]

Or for less than 5.

[oh_my_goodness]

lol good point.