13. Write a program, in which a user-defined function is used to judge whether an integer is a prime number. The main function inputs a number and outputs whether it is a prime number.

#include <math.h>
#include  <stdio.h>
int IsPrimeNumber(int number)
{	int i;
	if (number <= 1)	
		return 0;
	for (i=2; i<sqrt(number); i++)
	{	if ((number % i) == 0)	
			return 0; 	}
	return 1;}
 void main()
{ int n;
  printf(“Please input n:”);
  scanf(“%d”,&n);
  if(IsPrimeNumber(n))
     printf(“\n%d is a Prime Number”,n);
  else  printf(“\n%d is not a Prime Number”,n);}