We simply use the following divisibility rules,
A no. is divisible by 2 if it is even (ending in 0,2,4,6,8)
" 3 if the sum of the digits are divisible by 3
" 5 if the ones digit is 0 or 5
We perform continuous division
1) 2 | 48
2 | 24
2 | 12
2 | 6
3
So the prime factorization is 2⁴ x 3
2) 3 | 57
19
The prime factorization is 3 x 19
3) 5 | 125
5 | 25
5
The prime factorization is 5³
4) 2 | 90
3 | 45
3 | 15
5
The prime factorization is 2 x 3² x 5
5) 3 | 21
7
The prime factorization is 3 x 7
