a prime number
A prime number !
Any composite number will do. No primes!
composite number! ;)
49 has exactly 3 factors (1, 7, and 49) and is greater than 40 and less than 60.
That's a prime number.
The answer is 25 because it has the factors 1,5,25! :)
Any square of a prime number 13 or greater, like 169.