Which numbers have a least common multiple of 12?

Answer 1

Numbers for which the sum of the digits is divisible by 9. This is also true for 3. There are other divisibility/multiple tests for other numbers (e.g., numbers that are divisible by 5 end in 5 or 0; numbers whose last two digits are divisible by 4 are divisible by 4)

Answer 2

4 and 6 are one pair of numbers with an LCM of 12.

Answer 3

The twelve times table?