🔀📚Intermediate

Check Whether Number is Neon Number

Check if sum of digits squared equals number

A Neon Number is a number where the sum of digits of its square equals the number itself. For example, 9 is a neon number because 9² = 81 and 8 + 1 = 9.

📝 Examples

✓ 9 is Neon

9² = 81 → 8+1 = 9

✓ 1 is Neon

1² = 1 → 1 = 1

✗ 5 is NOT Neon

5² = 25 → 2+5 = 7 ≠ 5

✗ 12 is NOT Neon

12² = 144 → 1+4+4 = 9 ≠ 12

C Program to Check Neon Number

neon_number.c

1#include <stdio.h>
2
3int main() {
4    int num, square, sum = 0, digit;
5    
6    printf("Enter a number: ");
7    scanf("%d", &num);
8    
9    // Calculate square
10    square = num * num;
11    
12    // Sum digits of square
13    int temp = square;
14    while (temp > 0) {
15        digit = temp % 10;      // Get last digit
16        sum = sum + digit;      // Add to sum
17        temp = temp / 10;       // Remove last digit
18    }
19    
20    // Check if neon
21    if (sum == num) {
22        printf("%d is a Neon Number\n", num);
23        printf("%d² = %d, Sum of digits = %d\n", num, square, sum);
24    } else {
25        printf("%d is NOT a Neon Number\n", num);
26        printf("%d² = %d, Sum of digits = %d\n", num, square, sum);
27    }
28    
29    return 0;
30}

Output

Enter a number: 9

9 is a Neon Number

9² = 81, Sum of digits = 9

📖 Code Explanation

Code	Explanation
square = num * num	Calculate the square of the number
temp % 10	Extract the last digit
temp / 10	Remove the last digit
sum == num	Check if sum of digits equals original