#### Exercise 15

Write a Python program that asks the user to enter an integer n and determines whether n is prime or not.

#### Solution

# function to check if a number is prime def is_prime(n): if n < 2: return False for i in range(2, int(n**0.5) + 1): if n % i == 0: return False return True # main program n = int(input("Enter an integer: ")) if is_prime(n): print(n, "is a prime number") else: print(n, "is not a prime number")

__In this algorithm__:

**We define a function called is_prime:**that takes an integer n as an argument and returns True if n is prime and False otherwise.**The function checks if n is less than 2:**(since 0 and 1 are not prime), and then loops through all numbers from 2 to the square root of n, checking if any of them divide n evenly.**If a number is found that divides n evenly:**then n is not prime and the function returns False.**If the loop completes without finding a divisor for n:**then n is prime and the function returns True.**In the main program:**we first ask the user to enter an integer n using the input function and convert it to an integer using int.**Then, we call the is_prime function:**with n as an argument and print the result depending on whether n is prime or not.

**Younes Derfoufi**

**CRMEF OUJDA**

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