Divisibility Rule for 13
If you divide a number by 13 and you get a whole number as an answer (quotient), then that number is divisible by 13.
Instead of simply dividing your number by 13 to see if you get a whole number, you can use what we call the Divisibility Rule for 13.
The Divisibility Rule for 13 is used to determine if a number is divisible by 13. You can also call it the test of divisibility for 13.
You can determine if a number is divisible by 13 by grouping the numbers in blocks of three from right to left. Then, alternate subtracting and adding the numbers in the blocks. If the result is a multiple of 13, then the number is divisible by 13.
For example, in 1,604,824, you calculate 824 - 604 + 1= 221. Since 221 is divisible by 13, 1,604,824 is also divisible by 13.
However, 2,604,824 is not divisible by 13 because 824 - 604 + 2 = 222 and 222 is not divisible by 13.