The number 21 has only four factors: 1, 3, 7, and 21. Many number have more than four factors. Among them are 1x2x3x4x5 = 120.
Simply multiply four prime numbers with one another. If your number is too large, choose smaller factors. If your number is too small, choose larger factors. One possibility is 7 x 7 x 7 x 7. Other combinations are possible as well.
The number four.
Four of them which are: 1, 7, 13 and 91
1050.
If 21 is a factor of a number, then the factors of 21 must also be factors. So 3 and 7
The highest four digit number with 13 and 7 as common factors is 9919, which is equal to 13 x 763 and 7 x 1417.
2, 3, 5, 7 are the 4 prime factors Number is: 210
Any number that is the product of two primes (excluding itself and 1) has 4 factors. For example 21 has 4 factors: 1, 3, 7, 21; of which 3 and 7 are both prime.
14
3, 5 and 7 are factors of 105 15, 21, 35 and 105 are also factors of 105
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).