Which number is a factor of 12 but not a multiple of 3?

The number 4 is a factor of 12 because it divides evenly into 12 (12 ÷ 4 = 3), but it is not a multiple of 3, as 4 cannot be expressed as 3 times an integer. Therefore, 4 meets the criteria of being a factor of 12 while not being a multiple of 3.