Guess the number:

I am a composite number between 1 and 40.

I am a multiple of 3.

I am a factor of 48.

I have six factors.

The number is 12.

12 is a composite number.

12 is a multiple of 3 (12/3=4)

12 is a factor of 48 (48/12=4)

12 has six factors (1, 2, 3, 4, 6, and 12)

Multiples of three from one through 40-

3, 6, 9, 12, 15, 18, 21, 24, 27, 30, 33, 36, 39

The following numbers from above are factors of 48-

3, 6, 12, 24

The following numbers from above have six factors-

12 - 1,2,3,4,6,12

24 has more than six factors - 1, 2,3,4,6,8,12,24

So the number is twelve