You can put this solution on YOUR website! wich number is a prime number
1
12
99
:
1 is unusual because it seams like it should be prime, but the math gods decided it wasn't/
12=2*6, 3*4 so it's a composite number.
99=9*11,3*33 so it's a composite number as well
The only factors of 31 is 1*31 so it's prime.
Happy Calculating!!!