8+ CPP Prime Number Checker Program Examples

This post contains a total of 8+ Hand-Picked C++ Prime number checker Program Examples with Source Code. All these prime number checker programs are made using C++ Programming Language.

You can use the source code of these examples with credits to the original owner.

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C++ Prime Number Checker Programs

1. By Hatsy Rei

Made by Hatsy Rei. Simple C++ Program to check if a number is prime or not. Source

10
10 is prime : false
(Can be divided by 2)

#include <iostream>
int main()
{
    try
    {
        unsigned long long int x, y; 
         
        std::cin >> std::ws;
        if (char(std::cin.peek()) == '-') throw 1;
        
        std::cin >> x;
        if (std::cin.fail()) throw 0;        
    
        for (y = x%2?3:2; y*y<=x; y+=2) 
            if (!(x%y)) break;
        
        std::cout << std::boolalpha << x << " is prime : " << (((x%y)||(x==y))&&(!(x<2))) << std::endl;
    
        if (!(x%y)&&(!(x<4)))
            std::cout << "(Can be divided by " << y << ")";
    }
    catch (int err)
    {
        std::cout << (err ? "-ve values not allowed." : "Invalid input. D:");
    }     
    return 0;
}

2. By Jully Fredy

Made by Jully Fredy. Basic Prime number checker program. Source

Enter a positive integer: 12
You have entered: 12
12 is not a prime number

#include <iostream>
using namespace std;
int main(){
  int n, i;
  bool isPrime = true;

  cout << "Enter a positive integer: \n";
  cin >> n;

  for(i = 2; i <= n / 2; ++i){
      if(n % i == 0){
          isPrime = false;
          break;
      }
  }
  cout << "You have entered: "<<n<<"\n";
  if (isPrime)
      cout << n <<" is a prime number";
  else
      cout << n << " is not a prime number";
  return 0;
}

3. By AliReza

Made by AliReza. Source

input positive integer number
7
7 is prime number

#include <iostream>
using namespace std;
int main()
{
    int n;
    cin>>n;
    cout<<"input positive integer number\n"<<n<<" is ";
    if(n==2) cout<<"prime number";
    else if(n==1||n%2==0) cout<<"not prime number";
    else
 {
    for (int a=n-1;;a--)
   {
     if(a==1){cout<<"prime number"; break;}
     if(n%a==0){cout<<"not prime number"; break;}
   }
 }
   return 0;   
}

4. By Angelin Blessy

Made by Angelin Blessy. C++ Prime number checker program made using constructor. Source

Enter a number:34 
34 is not a prime number

#include <iostream>
using namespace std;
class prime
{
    int a,k,i;
    public:
    prime(int x)
    {
    a=x;
    }
    void calculate()
    {
        k=1;
        {
            for(i=2;i<=a/2;i++)
            if(a%i==0)
            {
                k=0;
                break;
            }
            else
            {
                k=1;
            }
        }
    }
    void show()
    {
        if(k==1)
        cout<<a<<" is a prime number";
        else
        cout<<a<<" is not a prime number";
    }
    
};
int main() 
{
int a;
cout<<"Enter a number:";
cin>>a;
prime obj(a);
obj.calculate();
obj.show();
return 0;
}

5. By Chris

Made by Chris. Source

enter a number
44
its not a prime number

#include <iostream>
using namespace std;
int main() 
{
    int num;
    cout<<"enter a number"<<endl;
    cin>>num;
    
    if(num <= 1)
        cout<<"its not a prime number";
    if(num == 2)
        cout<<"its a prime number";
    
    for(int x = 2; x < num; x++)
    {
        if(num % x == 0)
        {
            cout<<"its not a prime number";
            break;
        }
        if(x == num-1)
            cout<<"its a prime number";
    }
    
    return 0;
}

6. By Ayush Sinha

Made by Ayush Sinha. Basic prime number checker program. Source

33
It is not a prime number,in fact it is a composite number 

#include <iostream>
using namespace std;
string prime_checker(unsigned x){
    if(x<=1) return "It is neither a prime nor a composite number";
    for(unsigned i=2;i<x;i++){
        if (x%i==0) return "It is not a prime number,in fact it is a composite number ";
    }
    return "True,it is a prime number";
}
int main() {
    unsigned n;
    cin>>n;
    cout<<prime_checker(n);
    return 0;
}

7. By Ankit Saxena

Made by Ankit Saxena. Program to Check if a number is prime number using flag variable. Source

Enter a positive integer: 50
This is not a prime number

#include <iostream> 
using namespace std; 
int main() 
{ 
int n, i, flag; 
flag = 1; 
cout << "Enter a positive integer: "; 
cin >> n; 
for(i = 2; i <= n / 2; ++i) 
{ if(n % i == 0)
 { flag = 0; 
break; }
} 
if (flag==1)
 cout << "This is a prime number"; 
else cout << "This is not a prime number"; 
return 0; }

8. By Sudeep Jaiswal

Made by Sudeep Jaiswal. This C++ Program displays all the prime numbers in a given range. Like if you entered 100 then you will get all the prime numbers that come before 100. Source

10
The Prime Numbers Are: 
2
3
5
7
	

#include <iostream>
using namespace std;
int main() {
    int num,i,flag,n;
    cin>>n;
    cout<<"The Prime Numbers Are: ";
    for(num=1; num<=n; num++){
        flag=0;
        for(i=2;i<=num/2;i++){
            if(num%i==0){
                flag=1;
                break;
            }
        }
        if(flag==0 && num!=1)
            cout<<endl<<num;
    }
      cout<<endl<<"\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tCreated By Sudeep Jaiswal"<<endl<<"\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\t\tPlease Hit A Upvote";
    return 0;
}

9. By Kai

Made by Kai. Source

10
10 is not prime number

thank you 

#include <iostream>
using namespace std;

int main() {
     int n,i;
     int c=0;
     cin>>n;
     for( i=1;i<=n;i++)
     {
         if (n%i==0)
         c++;
     }
       if(c==2){
          cout<<n<<" is prime number";
       }
       else {
           cout<<n<<" is not prime number";
       }
    cout<<"\n\n\nthank you ";
     
    return 0;
}