NEON NUMBERS:

Any number whose sum of square is same as given number. 

p=9
sq=9*9=81                sum=8+1=9

neon number condition true. 

Program. 

#include<stdio.h>
int main()
{
    int j,i,p,n,sq,sum=0;
    printf("enter number: ");
    scanf("%d",&n);
    sq=n*n;
    printf("Square =%d",sq);
    for(i=sq; i>=1;)
    {
        j=i%10;
        sum=sum+j;
        i=i/10;
    }
    printf("\tsum=%d",sum);
    if(n==sum)
        printf("\nneon number ");
    else
        printf("\nnot a neon number");
    return 0;
}

OUTPUT :

enter number: 9
Square =81      sum=9
neon number
eg 2.
enter number: 7
Square =49      sum=13
not a neon number