C programming Question and Answer Day-15

71. Program to check Niven number (Harshad number).

#include<stdio.h>
#include<conio.h>
void main()
{
    int n, d, a, sum = 0;
    clrscr();
    printf("Enter the number : ");
    scanf("%d", &n);

    a = n;

    while (a > 0)
    {
        d = a % 10;
        sum = sum + d;
        a = a / 10;
    }

    if (n % sum == 0)
        printf("\nThe number is Niven Number.");
    else
        printf("\nThe number is not a Niven Number.");
    getch();
}

72. Program to check whether the number is palindrome or not.

#include<stdio.h>
#include<conio.h>
void main()
{
    int n, rev = 0, temp;
    clrscr();
    printf("Enter a number : ");
    scanf("%d", &n);

    temp = n;

    while (temp != 0)
    {
        rev = rev * 10;
        rev = rev + temp % 10;
        temp = temp / 10;
    }

    if (n == rev)
        printf("\n%d is palindrome number.", n);
    else
        printf("\n%d is not palindrome number.", n);
    getch();
}

73. Program to check perfect number.

#include<stdio.h>
#include<conio.h>

void main()
{
 int n, i = 1, sum = 0;
 clrscr();
 printf("Enter a number : ");
 scanf("%d", &n);

/The first perfect number is 6, because 1, 2, and 3 are its proper positive divisors, and 1 + 2 + 3 = 6./

 while (i < n)
 {
  if (n % i == 0)
  {
   sum = sum + i;
  }
  i++;
 }

 if (sum == n)
 {
  printf("\n%d is a perfect number.", i);
 }
 else
 {
  printf("\n%d is not a perfect number.", i);
 }
 getch();
}

74. Program to find the square root of a number.

#include<math.h>
#include<stdio.h>
#include<conio.h>
void main()
{
    double num, result;
    clrscr();
    printf("Enter number : ");
    scanf("%lf", &num);
    result = sqrt(num);
    printf("Square root of %lf is %lf.", num, result);
    getch();
}

75. Program to print sum of 'n' prime numbers.

#include<stdio.h>
#include<conio.h>
void main()
{
    int n, i = 3, count, c, sum = 2;
    clrscr();
    printf("Enter total number of prime numbers for addition : ");
    scanf("%d", &n);

    if (n >= 1)
    {
        printf("\nFirst %d prime numbers are :", n);
        printf("\n2 ");
    }
    for (count = 2; count <= n;)
    {
        for (c = 2; c <= i - 1; c++)
        {
            if (i % c == 0)
                break;
        }
        if (c == i)
        {
            sum = sum + i;
            printf("%d ", i);
            count++;
        }
        i++;
    }
    printf("\nSum : %d", sum);
    getch();
}