Program to check number is Prime or Not in C++

#include<bits/stdc++.h>
using namespace std;
bool isPrime(int num)
{
int p=num;
if(num%2==0)
return 0;
for(int i=3;i*i<=p;i+=2)
{
if(num%i==0)
return 0;
}
return 1;
}

int main()
{
int num=91;
cout<<isPrime(num);
}