In this post, we will learn how to check the perfect number using C++ Programming language.
A Perfect number is a positive integer that is equal to the sum of its positive divisors, excluding the number itself. For example: The divisors of 6 are 1, 2 and 3 such that 1 + 2 + 3 = 6. Hence, 6 is a perfect number.
We will be using following methods to check a perfect number:
- Using for loop
- Using while loop
- Using functions
So, without further ado, let’s begin this tutorial.
C++ Program to Check Perfect Number
// C++ Program to Check Perfect Number
#include <iostream>
using namespace std;
int main(){
int i, num, sum = 0;
// Asking for input
cout << "Enter any number: ";
cin >> num;
// Calculating sum of factors
for (i = 1; i < num; i++){
if (num % i == 0){
sum = sum + i;
}
}
// Checking perfect number
if (num == sum){
cout << num << " is a perfect number.";
}
else{
cout << num << " is not a perfect number.";
}
return 0;
}
Output 1
Enter any number: 6
6 is a perfect number.
Output 2
Enter any number: 12
12 is not a perfect number.
How Does This Program Work ?
int i, num, sum = 0;
In this program, we have declared three int data type variables named i, num and sum.
// Asking for input
cout << "Enter any number: ";
cin >> num;
Now, the user is asked to enter any positive number.
// Calculating sum of factors
for (i = 1; i < num; i++){
if (num % i == 0){
sum = sum + i;
}
}
We calculate the sum of all the divisors of the entered number.
if (num == sum){
cout << num << " is a perfect number.";
}
else{
cout << num << " is not a perfect number.";
}
Now, we check whether the sum of divisors is equal to the number itself or not. If yes, then the entered number is a perfect number otherwise the entered number is not a perfect number.
C++ Program to Check Perfect Number Using While Loop
// C++ Program to Check Perfect Number Using While Loop
#include <iostream>
using namespace std;
int main(){
int i = 1, sum = 0, num;
// Asking for input
cout << "Enter any number: ";
cin >> num;
// Calculating the sum of divisors
while (num > i){
if (num % i == 0){
sum = sum + i;
}
i++;
}
// Checking perfect number
if (num == sum){
cout << num << " is a perfect number.";
}
else{
cout << num << " is not a perfect number.";
}
return 0;
}
Output 1
Enter any number: 28
28 is a perfect number.
Output 2
Enter any number: 32
32 is not a perfect number.
C++ Program to Check Perfect Number Using Functions
// C++ Program to Check Perfect Number
#include <iostream>
using namespace std;
int perfect(int num){
int i = 1, sum = 0;
while (num > i){
if (num % i == 0)
sum = sum + i;
i++;
}
return(sum);
}
int main(){
int result, num;
// Asking for input
cout << "Enter a positive number: ";
cin >> num;
result = perfect(num);
// Checking perfect number
if (num == result){
cout << num << " is a perfect number.";
}
else{
cout << num << " is not a perfect number.";
}
return 0;
}
Output 1
Enter any number: 496
496 is a perfect number.
Output 2
Enter any number: 469
469 is not a perfect number.
Conclusion
I hope after going through this post, you understand how to check the perfect number using C++ Programming language.
If you have any doubt regarding the program, feel free to contact us in the comment section. We will be delighted to guide you.
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