- Write a C++ program to check whether a number is prime number or not.
- How to test whether a number is prime number(Primality testing).

## C++ Program to check Prime number

#include<iostream> using namespace std; int main() { int num, i, isPrime=0; cout << "Enter a Positive Integer\n"; cin >> num; // Check whether num is divisible by any number between 2 to (num/2) for(i = 2; i <=(num/2); ++i) { if(num%i==0) { isPrime=1; break; } } if(isPrime==0) cout << num << " is a Prime Number"; else cout << num << " is not a Prime Number"; return 0; }Output

Enter a Positive Integer 23 23 is a Prime Number

Enter a Positive Integer 21 21 is not a Prime Number