To find the factors of a number, you first need to split that number into its prime factors. In the case of 15, this produces:
15 = 3x5
The next step is to note that every factor of the number (apart from 1) is the product of any combination of its prime factors. Thus, the factors of 15 are:
1, 3, 5 and 15.
All of them. Different numbers have different numbers of factors.
12 does not have any factors under 1, factors are whole numbers.
48 is divisible by ten factors. There is an infinite amount of numbers divisible by 48.
Three factors in common.
Prime numbers have exactly two numbers. There is theoretically an infinite number of them.
Four
All of them. Different numbers have different numbers of factors.
Six of them.
The limit is infinity if the factors do not have to be whole numbers. If you stipulate that the factors have to be whole numbers, then, yes, for each number, there is a limit to how many factors it has. For example, the number 4 has only 3 whole-number factors: 1, 2, and 4.
Four of them.
1,2,4,8,16, so 5
Six numbers. They are 1, 2, 4, 5, 10 and 20.
There are infinitely many such numbers.
Four: 1 5 25 125.
14 (I think).
12 does not have any factors under 1, factors are whole numbers.
Its factors are: 1, 2, 4 and 8 which makes four of them