DIVISIBILITY RULES

A number is divisible by 2 if the number is even. In other words, if a number ends in 0, 2, 4, 6, or 8, then it is divisible by 2.

A number is divisible by 3 if the sum of the digits is divisible by 3. For example 141 is divisible by 3 because 1 + 4 + 1 = 6 and 6 is divisible by three. 364 is not divisible by 3 because 3 + 6 + 4 = 13 and 13 is not divisible by 3. Note that this rule can be used multiple times. For example, to check if 135,593,334,384 is divisible by 3, we add 1 + 3 + 5 + 5 + 9 + 3 + 3 + 3 + 4 + 3 + 8 + 4 = 51. To check that 51 is divisible by 3, we add 5 + 1 = 6. 6 is divisible by 3, so 51 is divisible by 3, so 135,593,334,384 is divisible by 3.

A number is divisible by 4 if the number formed by the last two digits is divisible by 4. For example, 2,356 is divisible by 4 since 4 divides 56 evenly. Alternatively, a number is divisible by four if the quotient of the number and 2 is even. In the previous example 2,356 2 = 1178 which is even.

A number is divisible by 5 if the number ends in a 0 or 5.

A number is divisible by 6 if the number is divisible by 2 and is divisible by 3.

A number is divisible by 9 if the sum of the digits is divisible by 9. This rule is similar to the divisibility rule for 3.

A number is divisible by 10 if the number ends in a 0.