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 "))
