A Python program to check if a given number is prime or not

A prime number is a positive integer greater than 1 that has no positive integer divisors other than 1 and itself. In other words, a prime number is a number that can only be evenly divided by 1 and itself.

For example, 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, and 31 are the first few prime numbers. Note that 1 is not considered a prime number, as it only has one positive divisor (1) and does not meet the definition of a prime number.

 Here's a Python program to check if a given number is prime or not:

python
# Function to check if a number is prime
def is_prime(n):
    if n <= 1:
        return False
    for i in range(2, int(n**0.5) + 1):
        if n % i == 0:
            return False
    return True

# Get the number to check from the user
num = int(input("Enter a number: "))

# Check if the number is prime
if is_prime(num):
    print(num, "is a prime number")
else:
    print(num, "is not a prime number")

In this program, I first define a function is_prime() to check if a number is prime or not. This function takes a number n as input and returns True if it's prime, or False if it's not.

I then ask the user to enter a number to check. I call the is_prime() function on the number, and print a message indicating whether it's prime or not based on the function's return value.

Note that I use the square root of n to limit the number of divisors I need to check in the is_prime() function, as any factor of n greater than sqrt(n) must have a corresponding factor less than sqrt(n) to form a pair.