Posted by makeeda on .
which of following is not a prime number?
A)17
B)23
C)31
D)51

math 
Luv4ever,
What do you think? First of all go on to Google and look up prime numbers. You'll get a way better understanding of them in a small amount of time. I'll give you one hint: 51 is a prime number because 3 and 17 are it's factors.

math 
PsyDAG,
Luv4ever has a typo.
51 is NOT a prime number because 3 and 17 are it's factors.