Python Program to find Prime Number or Not using For Loop

Before going to the program for Prime Number or Not first let us understand what is a Prime Number?

Prime Number:

                 A Prime Number is a number greater than 1 and which is only divisible by 1 and the number itself.

For example,

                17 is a Prime Number because 17 is not divisible by any number other than 1 and 17.

To find whether a Number is Prime Number or Not it is enough to check whether ‘n’ is divisible by any number between 2 and √n. If it is divisible then ‘n’ is not a Prime Number otherwise it is a Prime Number.

Related: C Program to display Prime Numbers between Two Intervals

Program code for Prime Number or Not in Python:

# Python Program to check if a number is prime or not
from math import sqrt

# To take input from the user
num = int(input("Enter a number: "))

# define a flag variable
prime_flag = False

# prime numbers are greater than 1
if num > 1:
    for i in range(2, int(sqrt(num)) + 1):
        if (num % i) == 0:
            prime_flag = True

# check if flag is True
if prime_flag:
    print(num, "is not a prime number")
    print(num, "is a prime number")

Related: Prime number or Not in C++ using While Loop


  • First, the computer reads the positive integer value from the user.
  • Then using for loop it checks whether ‘n’ is divisible by any number between 2 and √n.
  • Finally, the if else condition is used to print whether the number is a prime number or not.


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