Prime Number Tester

import math, sys, time
while True:
    print('Enter a number that you want to check if it is prime.')
    number = eval(input())
    try:
        if number == 1:
            print('That number is not prime because mathematicians say so')
        elif number % 2 != 0:
            nnumber = int(round(number / 2 , 0))
            for i in range(3, nnumber + 1):
                if number % i == 0:
                    prime = 0
                    print('That number is not a prime number because it is divisible by ' + str(i) + '.')
                    break
                elif number % i != 0 and i == nnumber:
                    print('That number is a prime number')
        elif number == 2:
            print('That number is a prime number')
        else:
            print('That number is not a prime number because it is divisible by 2')
    except OverflowError:
        for i in range(2, number):
            if number % i != 0:
                prime = 1
                continue
            else:
                prime = 0
                print('That is not a prime number becuase it is divisible by ' + str(i) + '.')
                break
        if prime == 1:
            print('That number is a prime number.')