Divisibility rules:
-> A number is
divisible by 2 if and only if the last digit is divisible by 2.
-> A number is divisible by 3 if and only if the sum of the digits is divisible by 3.
-> A number is divisible by 4 if and only if the last 2 digits is a number divisible by 4.
-> A number is divisible by 5 if and only if the last digit is divisible by 5.
-> A number is divisible by 6 if and only if it is divisible by 2 and 3.
-> A number is divisible by 8 if and only if the last 3 digits is a number divisible by 8.
-> A number is divisible by 9 if and only if the sum of the digits is divisible by 9.
-> A number is divisible by 10n if and only if the number ends in n zeros.
-> A number is divisible by 11 iff the sum of every other digit minus the sum of the rest of the digits is divisible by 11.
-> To find out if a number is divisible by seven, take the last digit, double it, and subtract it from the rest of the number.Example: If you had 203, you would double the last digit to get six, and subtract that from 20 to get 14. If you get an answer divisible by 7 (including zero), then the original number is divisible by seven. If you don't know the new number's divisibility, you can apply the rule again.
-> If n is even , n(n+1)(n+2) is divisible by 24
-> A number is divisible by 3 if and only if the sum of the digits is divisible by 3.
-> A number is divisible by 4 if and only if the last 2 digits is a number divisible by 4.
-> A number is divisible by 5 if and only if the last digit is divisible by 5.
-> A number is divisible by 6 if and only if it is divisible by 2 and 3.
-> A number is divisible by 8 if and only if the last 3 digits is a number divisible by 8.
-> A number is divisible by 9 if and only if the sum of the digits is divisible by 9.
-> A number is divisible by 10n if and only if the number ends in n zeros.
-> A number is divisible by 11 iff the sum of every other digit minus the sum of the rest of the digits is divisible by 11.
-> To find out if a number is divisible by seven, take the last digit, double it, and subtract it from the rest of the number.Example: If you had 203, you would double the last digit to get six, and subtract that from 20 to get 14. If you get an answer divisible by 7 (including zero), then the original number is divisible by seven. If you don't know the new number's divisibility, you can apply the rule again.
-> If n is even , n(n+1)(n+2) is divisible by 24
