Question: what are all the divisibility rules?
Answer: Any integer (not a fraction) is divisible by 1. The last digit is even (0,2,4,6,8) ...  The sum of the digits is divisible by 3. ...  The last 2 digits are divisible by 4. ...  The last digit is 0 or 5. ...  Is even and is divisible by 3 (it passes both the 2 rule and 3 rule above)