Java Program to Check a Number is Prime Number or Not

Here is a java program to check, whether a number is prime number or not. We have to check whether given number is prime number or not. First of all, we have to understand fundamentals of prime numbers.

  • A Prime number is a positive number greater than 1 that is only divisible by either 1 or itself.
  • All numbers other than prime numbers are known as composite numbers.
  • Any non-prime number can be expressed as a factor of prime numbers.
  • There are infinitely many prime numbers, here is the list of first few prime numbers
    2 3 5 7 11 13 17 19 23 29 31 37....

Java program to check for prime number

Let N be the number for primality testing. Here, we will use brute force approach by testing whether N is a multiple of any integer between 2 and N/2. This is the most basic method of checking the primality of a given integer N and is called trial division method.

import java.util.*;

public class PrimeNumberCheck {
    public static void main(String args[]) {
        int num, i, isPrime = 0;
        Scanner in = new Scanner(;

        System.out.println("Enter an Integer");
        num = in.nextInt();

        for(i = 2; i <= (num / 2); ++i) {
            if (num % i == 0) {
                isPrime = 1;
        if (isPrime == 0)
            System.out.println(num + " is a Prime Number");
            System.out.println(num + " is not a Prime Number");
Enter an Integer
23 is a Prime Number
Enter an Integer
30 is not a Prime Number

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