Question

A certain number has exactly 8 factors including 1 and itself. 2 of its factors are 21 and 35 what is the number?

Answer 1

21 = 3.7
35 = 5.7

probably the factors have 3.5.7
= 105

let's try :
1 . 105
3 . 35
5 . 21
7 . 15
Yep, correct.