... oh, I see : 4 = 1, 2 and 4
25 = 1, 5 and 25
...sorry,
É.
> 21 = 1*3*7
> 22 = 1*2*11
> Is it true that all numbers with exactly three divisors,
with the exception only of 4 and 25, have either 1 or 9 as their last
decimal digit?