what are all the divisibility rules?
['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)']