title: Built in prime checking function
body: <p>Does C++ have any built in function to check if the number is prime or not. If yes, then in which library?</p>
  
  <p>Below is my implementation. But was just looking if there is any built in function. Searching on Google just gives user based implementations.</p>
  
  <pre><code>int isprime(int N){
      if(N&lt;2 || (!(N&amp;1) &amp;&amp; N!=2))
          return 0;
      for(int i=3; i*i&lt;=N; i+=2){
          if(!(N%i))
              return 0;
      }
      return 1;
  }
  </code></pre>