Is 516 divisible by 9

Answer 1

To be divisible by 9, sum the digits of the number and if this sum is divisible by 9, then the original number is divisible by 9.

As the test can be repeated on the sum, repeat the summing until a single digit remains; only if this number is 9 is the original number divisible by 9.

For 516 this gives:

→ 5 + 1 + 6 = 12

→ 1 + 2 = 3

3 is not 9 so 516 is not divisible by 9.

(This single digit is known as the digital root of the number.)