Divisibility Rules

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Divisibility Rules
An integer N is evenly divisible by
2
if the last digit is even (0, 2, 4, 6, or 8);
Example: 123,456 is divisible by 2, because the last digit, 6, is even.
3
if the sum of its digits is divisible by 3;
Example: 123,456 is divisible by 3, because 1 + 2 + 3 + 4 + 5 + 6 = 21, which is divisible by 3. (21
÷ 3 = 7)
4
if the number formed by the two last digits is divisible by 4;
Example: 123,456 is divisible by 4, because 56 is divisible by 4.
(56 ÷ 4 = 14)
5
if it ends in 5 or 0;
Examples:
123,456 is not divisible by 5, because the last digit, 6, is not 0 or 5.
12,345 is divisible by 5, because the last digit is 5.
6
if it is divisible by both 2 and 3;
Example: 123,456 is divisible by 6, since it is divisible by both 2 and 3. (See examples for 2 and
3 above.)
7
if the number formed after the following two steps is divisible by 7:
 First, remove the last digit,
 Then, from the number remaining, subtract two times the digit we just removed;
See examples on the back of this page.
8
if the number formed by the last three digits is divisible by 8;
Example: 123,456 is divisible by 8, because 456 is divisible by 8.
(456 ÷ 8 = 57)
9
if the sum of its digits is divisible by 9;
Examples:
123,456 is not divisible by 9, since 1 + 2 + 3 + 4 + 5 + 6 = 21 is not divisible by 9.
123,453 is divisible by 9, since 1 + 2 + 3 + 4 + 5 + 3 = 18 is divisible by 9. (18 ÷ 9 = 2)
10
if it ends in 0;
Examples:
123,456 is not divisible by 10, since its last digit, 6, is not 0.
123,450 is divisible by 10, since its last digit is 0.
11
for two-digit numbers, if it is double,
Examples: 11, 22, 33, 44, 55, 66, 77, 88, and 99 are each divisible by 11.
for larger numbers, if the number formed after the following three steps is divisible by 11:
 find the sum of alternate digits,
 find the sum of the remaining digits,
 find the difference of these two sums;
See examples on the back of this page.
12
if it is divisible by both 3 and 4.
Example: 123,456 is divisible by 12, since it is divisible by both 3 and 4.
(See examples for 3 and 4 above.)

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