Code: 
#include <iostream>
using namespace std;
bool prime(int n)
{
	if (n<=1)
	{
		return false;
	}
       for (int i=2;i<=n/2;i++)
	   {
	      if (n%i==0)
		  {
		  	return false;
		  }	
	   }	   
    return true;
}
int nearest(int n)
{
		for (int i=n-1;i>=2;i--)
		{
			if (prime(i))
			{
				return i;
			}
		}
	return 0;
}
int main ()
{
	int number;
	cout<<"Enter any number : ";
	cin>>number;
	if (prime(number))
	{
		cout<<"The number is prime. "<<endl;
	}
    else
    {
    	cout<<"The entered number is compositive."<<endl;
    	cout<<"The nearest prime number will be "<<nearest(number)<<endl;
	}
}
Result:

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