Q. Write a program to Check Whether a Number is Prime or not?

Solution :- This program is about giving a positive integer N and the task is to check whether the number N is prime or not.

Prime Number:-A number that is divisible by only and only 1 and itself is known as a Prime Number. For example: - 11 is only divisible by 1, so 11 is prime, while 10 is divisible by 1, 2, and 5 so 10 is not a prime number. .

Prime Number Algorithm

START
  Step 1 → Take integer variable A
  Step 2 → Divide the variable A with (A/2 to 2)
  Step 3 → If A is divisible by any value (A/2 to 2) then it is not prime
  Step 4 → Else it is prime number
STOP


Prime Number Program

  • C
  • C++
  • Java
  • Python
  • PHP
  • #include <stdio.h>
    int main() {
        int n, i, flag = 0;
        printf("Enter a positive integer: ");
        scanf("%d", &n);
    
        for (i = 2; i <= n / 2; ++i) {
    
            // condition for non-prime
            if (n % i == 0) {
                flag = 1;
                break;
            }
        }
    
        if (n == 1) {
            printf("1 is neither prime nor composite.");
        }
        else {
            if (flag == 0)
                printf("This is a prime number.");
            else
                printf("This is not a prime number.");
        }
    
        return 0;
    }
    
    #include <iostream>
    using namespace std;
    
    int main()
    {
      int n, i;
      bool isPrime = true;
    
      cout << "Enter a positive integer: ";
      cin >> n;
    
      for(i = 2; i <= n / 2; ++i)
      {
          if(n % i == 0)
          {
              isPrime = false;
              break;
          }
      }
      if (isPrime)
          cout << "This is a prime number";
      else
          cout << "This is not a prime number";
    
      return 0;
    }
    
    import java.util.Scanner;
    class PrimeCheck
    {
       public static void main(String args[])
       {    
      int temp;
      boolean isPrime=true;
      Scanner scan= new Scanner(System.in);
      System.out.println("Enter a positive number:");
      //capture the input in an integer
      int num=scan.nextInt();
            scan.close();
      for(int i=2;i<=num/2;i++)
      {
               temp=num%i;
         if(temp==0)
         {
            isPrime=false;
            break;
         }
      }
      //If isPrime is true then the number is prime else not
      if(isPrime)
         System.out.println(num + " is a Prime Number");
      else
         System.out.println(num + " is not a Prime Number");
       }
    }
    
    
    # To take input from the user
    num = int(input("Enter a positive integer: "))
    
    # prime numbers are greater than 1
    if num > 1:
       # check for factors
       for i in range(2,num):
           if (num % i) == 0:
              
               break
       else:
           print(num,"is a prime number")
           
    # if input number is less than
    # or equal to 1, it is not prime
    else:
       print(num,"is not a prime number")
    
    
    function primeCheck($number){ 
        if ($number == 1) 
        return 0; 
        for ($i = 2; $i <= $number/2; $i++){ 
            if ($number % $i == 0) 
                return 0; 
        } 
        return 1; 
    } 
      
    // Driver Code 
    $number = 31; 
    $flag = primeCheck($number); 
    if ($flag == 1) 
        echo "31 is a prime number."; 
    else
        echo "31 is Not a prime number."
    
    #include <stdio.h>
    int main() {
        int n, i, flag = 0;
        printf("Enter a positive integer: ");
        scanf("%d", &n);
    
        for (i = 2; i <= n / 2; ++i) {
    
            // condition for non-prime
            if (n % i == 0) {
                flag = 1;
                break;
            }
        }
    
        if (n == 1) {
            printf("1 is neither prime nor composite.");
        }
        else {
            if (flag == 0)
                printf("This is a prime number.");
            else
                printf("This is not a prime number.");
        }
    
        return 0;
    }
    

    Output

    Enter a positive integer : 17
    This is a prime number.
    
    Enter a positive integer : 25
    This is not a prime number.
    

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