In this C++ programming example, we will learn about the prime number program in C++. We specifically write a program to check the entered number is prime or not. Let us start by understanding what is a prime number.
A Prime Number is a number that is only divisible by 1 and itself. Example: 2, 3, 5, 7, 11, 13, 17, etc. These numbers are only divisible by 1 and the number itself.
0 and 1 is not a prime number and 2 is the only even and smallest prime number.
To understand the following program, you should have a basic idea about the following topics in C++ programming.
Check Prime Number in C++
The program takes a user input for a number that needed to be checked for prime number. Since 0 and 1 are not prime numbers so we first check them using the if statement. And if the number is other than 0 and 1 the execution control goes to the else part of the statement.
C++ Program to Check Whether a Number is Prime or Not
using namespace std;
int i, num, flag;
cout << "Enter a positive integer: ";
cin >> num;
// checking for 0 and 1
if (num == 0 || num == 1)
flag = 1;
for (i = 2; i <= num / 2; ++i)
if (num % i == 0)
flag = 1;
if (flag == 0)
cout << num << " is a prime number";
cout << num << " is NOT a prime number";
Enter a positive integer: 13
13 is a prime number
You may go through the following program of prime numbers in C++.
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