Question

A prime number is a number that is only evenly divisble by itself and 1.
For example, the number 5 is prime because it can only be evenlly divided by 1
and 5. The number 6, however, is not prime because it can be divided evenly
by 2 and 3.

Write a Boolean function named is_prime which takes an integer as an argument
and returns true if the argument is a prime number, or false otherwise. Use
the function in a program that prompts the user to enter a number and then
prints whether the number is prime.

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 "))