# C++ Example – C++ program to find prime numbers

Prime Numbers
A prime number is an integer greater than 1 that has exactly two divisors, 1 and itself.
The first ten prime numbers are

• 2, 3, 5, 7, 11, 13, 17, 19, 23, and 29.

Integers that are not prime are called composite numbers.
C++ program to find prime numbers in a given range

```#include <iostream>
#include <iomanip>      // std::setw

using namespace std;

int main()
{
int num,i,count,n;
cout << "Enter max range: ";
cin >> n;
for(num = 1;num<=n;num++){
count = 0;
for(i=2;i<=num/2;i++){
if(num%i==0){
count++;
break;
}
}

if(count==0 && num!= 1)
cout << num << setw(3);
}
return 0;
}

/*
OUTPUT:
Enter max range: 30
2  3  5  7 11 13 17 19 23 29
*/
```

C++ Program to Check If the number is Prime or not

```#include <iostream>

using namespace std;

int main()
{
int i,no;
cout<<"Enter any num: ";
cin>>no;
if(no==1)
{
cout<<"Smallest prime num is 2";
}
for(i=2;i<no;i++)
{
if(no%i==0)
{
cout<<"Not prime number";
break;
}
}
if(no==i)
{
cout<<"Yes, Number is Prime";
}
return 0;
}

/*
OUTPUT:
Enter any num: 17
Yes, Number is Prime
*/
```

C++ Program to Print next Prime number

```#include <iostream>

using namespace std;

int main()
{
int i,j=2,number;
cout<<"Enter any number: ";
cin>>number;
cout<<"Next prime number: ";
for(i=number+1;i<3000;i++)
{
for(j=2;j <i;j++)
{
if(i %j==0)
{
break;
} // if
} // for
if(i==j || i==1)
{
cout<<"\t"<<i;
break;
} // if
}  // outer for
return 0;
}

/*
OUTPUT:
Enter any number: 17
Next prime number:      19

*/
```