In this article, you will learn a C++ program to check prime numbers. The concept of prime numbers is very clear. All the positive integers that are divisible by 1 and themselves are called prime numbers.

If we have a number 17. It’s a prime number because it is divisible by 1 and itself. While on the other hand 25 is not a prime number as it is divisible by 1, 5, and 25.

The list of the first 10 prime numbers are:

`2, 3, 5, 7, 11, 13, 17, 19, 23, 29`

Here we discuss two different examples to check prime numbers in C++.

**Check prime numbers in C++****Display prime number between two intervals**

**Example 1: Check prime numbers in C++**

In this example, the program takes any number from the user and finds whether the entered number is prime or not.

```
//C++ program to check prime numbers
#include<iostream>
using namespace std;
int main()
{
int number, i, check=0;
cout<<"Enter Any Number: ";
cin>>number;
for(i=2; i<number; i++)
{
if(number%i==0)
{
check++;
break;
}
}
if(check==0)
cout<<number<<" is a Prime Number";
else
cout<<number<<" is not a Prime Number";
cout<<endl;
return 0;
}
```

### Output

**Example 2: Display prime numbers between two intervals**

In this example, the program takes two intervals from the user, and the program displays all the prime numbers between these intervals. Check the code below.

```
//C++ program to check prime numbers between two intervels
#include<iostream>
using namespace std;
int main()
{
int intervel1, intervel2, num, i, j;
cout<<"Enter First Intervel: ";
cin>>intervel1;
cout<<"Enter Second Intervel: ";
cin>>intervel2;
cout<<"Prime Numbers between "<<intervel1<<" and "<< intervel2<<" are";
for (i = intervel1 + 1; i < intervel2 ; ++i){
num = 0;
for (j = 2; j <= i/2; ++j){
if (i % j == 0){
num = 1;
break;
}
}
if (num == 0){
cout<<"\n"<<i;
}
}
return 0;
}
```