Question

What is a number that is greater than 5 and less than 40, is not divisible by 2, the sum of it's digits is 7 and has exactly 3 factors?

Answer 1

Is odd between 5 and 40 is a square number and the digits add to 7.
all the square numbers between there are 9,16, 25, 36
It's not 9, 16 or 36 so it has to be 25 

Hope this helps :)