Question

A prime number is a number that is only evenly divisble by itself and 1.

Answer 1

Let's be honest, there are plenty of solutions on the internet. Here's one where I added a program to use it. Note that this one is optimized to not consider even numbers, and to only iterate to the squareroot of the number you're testing.

def is_prime(n):

   if n == 2 or n == 3: return True

   if n % 2 == 0 or n < 2: return False

   for i in range(3, int(n**0.5)+1, 2):  

       if n % i == 0:

           return False

   return True

x = int(input("Enter a number: "))

print("{} is {}a prime.".format(x, "" if is_prime(x) else "not "))