Perfect number in C, Pyramid pattern, Number is power of two or not and Sum of series in c programming

Write a C program to check whether a given number (N) is a perfect number or not?
[Perfect Number - A perfect number is a positive integer number which is equals to the sum of its proper positive divisors. For example 6 is a perfect number because its proper divisors are 1, 2, 3 and it’s sum is equals to 6.]

#include <stdio.h>
int main()
{
    int N;
    scanf("%d",&N);
int i, sum=0;
    for(i=1; i<N;i++)
    {
        if(N%i==0)
            sum+=i;
    }

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

	Input	Output
	8000	8000 is not a perfect number.
	8128	8128 is a perfect number.
	6	6 is a perfect number.
	87	87 is not a perfect number.

Write a C program to find sum of following series where the value of N is taken as input 1+ 1/2 + 1/3 + 1/4 + 1/5 + .. 1/N

#include<stdio.h>

int main()

{

int N;

float sum = 0.0;

scanf("%d",&N);

int i;

for(i=1;i<=N;i++)

sum = sum + ((float)1/(float)i);

printf("Sum of the series is: %.2f\n",sum);

}

	Input	Output
	100	Sum of the series is: 5.19
	20	Sum of the series is: 3.60
	6	Sum of the series is: 2.45
	50	Sum of the series is: 4.50

Write a C program to check whether the given number(N) can be expressed as Power of Two (2) or not.
For example 8 can be expressed as 2^3. 

#include <stdio.h>

int main()

{

    int N;

    scanf("%d",&N);

int temp, flag;

    temp=N;

    flag=0;

   

    while(temp!=1)

    {

        if(temp%2!=0){

            flag=1;

            break;

        }

        temp=temp/2;

    }

  

    if(flag==0)

        printf("%d is a number that can be expressed as power of 2.",N);

    else

        printf("%d cannot be expressed as power of 2.",N);

}

	Input	Output
	6572	6572 cannot be expressed as power of 2.
	1024	1024 is a number that can be expressed as power of 2.
	8	8 is a number that can be expressed as power of 2.
	46	46 cannot be expressed as power of 2.

Write a C program to print the following Pyramid pattern upto Nth row. Where N (number of rows to be printed) is taken as input.*****
****
***
**
*

#include<stdio.h>

int main()

{

int N;

scanf("%d", &N); /*The value of N is taken as input from the test case */

int i,j;

for(i=N; i>0; i--)

  {

  for(j=0;j<i;j++)

    {

    printf("*");

    }

  printf("\n");

  } 

}

	Input	Output
	7	******* ****** ***** **** *** ** *
	4	**** *** ** *
	5	***** **** *** ** *
	3	*** ** *