What 4-digit number is divisible by 3?

3333
6666
9999

To see what 4 digit numbers are divisible by 3, you add the 4 digit number's digits together.

If those 4 numerals added together can be divided by 3, then the whole number is divisable by 3...for example, with the first two numbers divisible by three:

In the number 1002, the 1 and the 2 equals 3. That means the whole number is divisible by 3.

As well, the next number divisible by 3 is 1005. That's because the 1 and 5 equals 6 and 6 is divisible by 3 so the whole number is divisible by 3.

This works all the way up to the last two 4 digit numbers divisible by 3 which are. 9996 (9+9+9+6=33 which is divisible by 3)  and as Ancient Hippy's answer says, 9999.

6666