What is divisibility rule for 3

Since 18 is divisible by 9, 9 is a factor of 18. A divisibility test is a rule for determining whether one whole number is divisible by another. It is a quick way to find factors of large numbers. Divisibility Test for 3: if the sum of the digits of a number is divisible by 3, then the number is divisible by 3.

Add all the digits of the number you are checking. if this number is divisible by 3 then the original number is too

example is 16344 divisible by 3?

1+6+3+4+4=18. 18 is divisible by three, so 16344 is divisible by three also