how to determine a prime number:

A Natural Number is Divisible by

2 :If the Number is Even

3 :If the Sum of the Digits is divisible by 3

4 :If the last 2 digits is a number divisible by 4

5 :If the last digit is 5 or 0

6 :If the Number is even and divisible by 3

8 :If the number is divisible by 4 and the result is even

9 :If the sum of its digits is divisible by 9

10 :If the last digit is 0

that's all. thankew.