replace your prime function with this matt

//Prime function
void* Prime(void* index){
  int temp_index;

  temp_index = *((int*)index);
  long  sum_t = 0;

  for(long i = start_numbers[temp_index]; i <= numbers[temp_index]; i++){

      // Corner cases

      if(i<=1)continue;
      if (i <= 3){
            sum_t++;
            continue;
      }


      for (int j=2; j*j <= i; j++)
      {
          if ((i % j == 0) ||  (i %( j+2))==0 )
          {
              break;
          }
          else if (j+1 > sqrt(i)) {
              sum_t++;
          }
       }

  }

    cout << "Thread " << temp_index << " terminates" << endl;
    pthread_exit( (void*) sum_t);
}