Question: is 25 prime and why?
Answer: For 25, the answer is: No, 25 is not a prime number. The list of all positive divisors (i.e., the list of all integers that divide 25) is as follows: 1, 5, 25. For 25 to be a prime number, it would have been required that 25 has only two divisors, i.e., itself and 1.