How can you tell if a large number is divisible by 6?
If an even number is divisible by 3, then it must be divisible by 6. For example, 1332 is even, and 1+3+3+2 = 9, which is divisible by 3, so 1332 must be divisible by 3. Since 1332 is both even and divisible by 3, it must be divisible by 6 as well.