fastest way to check if a number is prime c++ code example

Example: check prime cpp gfg

bool isPrime(int s){
   if(s<=1)return false;
   if(s==2)return true;
   int m = ceil(sqrt(s));
   for(int i=2;i<=m;i++){
       if(s%i==0){
           return false;
       }
   }
   return true;
}