How I write a code to know prime number by if .

public class PrimeNumDemo3
{
  public static void main(String as[ ])
  {
     int number=6;
	 int varynum=0;
	 
	
	 if(int i=1;i<=number;i++)
       {
         if(num%i==0)
		 {
			varynum++;
		 }
       }
	   if(varynum==2)
	   {
		  System.out.println("number prime"); 
	   }
   
 else
   { 
    System.out.println("nt prime");

  }
 
}
}