# C program to Check a Number is a Neon Number

Write a c program to check a number is a neon number or not using the for loop. If the number equals the sum of digits of the square of a number, it is a neon number.

1. We use the math pow function to find the square of a number.
2. Divide the output into individual digits and calculate the sum of it.
3. The if else to check whether the sum of digits in a square equals the actual number. If true, it is a neon number.
```/* C program to Check a Number is a Neon Number using For loop */
#include <stdio.h>
#include<math.h>

int main()
{
int Number, squr, rem, Sum;

printf("Enter Number to Check = ");
scanf("%d", &Number);

squr = pow(Number, 2);

for (Sum = 0; squr > 0; squr = squr / 10)
{
rem = squr % 10;
Sum = Sum + rem;
}

if (Number == Sum)
printf("\n%d is a Neon Number.\n", Number);
else
printf("\n%d is not.\n", Number);
}
```

This C program checks whether the given number is a neon number or not using a while loop.

```#include <stdio.h>
#include<math.h>

int main()
{
int Number, squr, rem, Sum = 0;

printf("Enter Number to Check = ");
scanf("%d", &Number);

squr = pow(Number, 2);
printf("The Square of a Number %d = %d\n", Number, squr);

while(squr > 0)
{
rem = squr % 10;
Sum = Sum + rem;
squr = squr / 10;
}
printf("The Sum of Digits in a Square = %d\n", Sum);
if (Number == Sum)
printf("\n%d is a Neon Number.\n", Number);
else
printf("\n%d is not.\n", Number);
}
```
``````Enter Number to Check = 9
The Square of a Number 9 = 81
The Sum of Digits in a Square = 9

9 is a Neon Number.``````

In this C check neon number example, the squareDigitsSum recursive function divide and find the sum by calling it recursively.

```#include <stdio.h>
#include<math.h>

int squareDigitsSum(int num)
{
static int rem, sum = 0;

if(num > 0)
{
rem = num % 10;
sum = sum + rem;
squareDigitsSum(num / 10);
}
return sum;
}

int main()
{
int Number;

printf("Enter Number to Check = ");
scanf("%d", &Number);

int squr = pow(Number, 2);

int Sum = squareDigitsSum(squr);

printf("The Square of %d Number = %d\n", Number, squr);

printf("The Sum of Digits in %d = %d\n", squr, Sum);

if (Number == Sum)
printf("\n%d is a Neon Number.\n", Number);
else
printf("\n%d is not.\n", Number);
}
```
``````Enter Number to Check = 5
The Square of 5 Number = 25
The Sum of Digits in 25 = 7

5 is not.``````