C Program to Detection of a Prime Number

How to write a C Program to Detection of a Prime Number in C Programming Language ?

Write a program to determine whether a number is prime or not. 

Note :A prime number is one, which is divisible only by 1 or itself. 

1. #include<stdio.h>
2. main()
3. {
4. int num, i;
5.  
6. printf ("Enter a number:");
7. scanf ("%d", &num);
8.  
9. i=2;
10. while (i<=num - 1)
11.  
12. {
13. if (num % i ==0)
14.  
15. {
16. printf ("Not a prime number");
17. break;
18. }
19.  
20. i++;
21. }
22.  
23. if (i == num)
24.  
25. printf ("Prime Number");
26. }

C Program to Check Whether Number Is Perfect Or Not

How to Write A C Program Whether a Number Is Perfect Or Not ?

Solution:

1. #include<stdio.h>
2. int main()
3. {
4.     int number,sum=0,i;
5.     scanf("%d", &number);
6.  
7.     for(i=1; i<=number/2; i++) {
8.         if(number%i==0) {
9.             sum = sum + i;
10.         }
11.     }
12.     if(sum==number) {
13.         printf("Perfect Number");
14.     }
15.     else {
16.         printf("Not");
17.     }
18. }