36
If you mean 2, 3 and 7 as factors then the smallest number is 42
The smallest number that has 9 and 12 as factors is 36.
That number is 724.
4096
The smallest prime factors are 2,3,5,7 thus the smallest number would be the product of these will be 210
12
Logically, the smallest number with 4 different prime factors would have to be the product of the smallest four prime numbers. So the smallest natural number with four different prime factors is 210 (2*3*5*7).
I think that it is 4
36
How about: 105
1155
6: 1, 2, 3, 6
60
It is: 44
36
the answer would seem to be ten.