no segment, how redirect 404 ?

Your project routes never know about 19999999 is in your project(database).
So all you have to do is catch those with controller

In customer Controller

Code:

    public function card($value)
    {
        # then here write an select Query
        #ex
        $result = $this->model_name->check_value($value);
        if ($result == false) {
            # Show 404 page. I you have created custom page in view, Then use load->view().
            # If not use default
            show_404();
        }
        else{
            # Continue with your rest of code
        }
    }

In Model

Code:

    public function check_value($value)
    {
        $query = $this->db->query("SELECT * FROM table_name WHERE filed = $value ");
        $result = $query->result_array();

        $count = count($result);

        if (empty($count)) {
            return false;
        }
        else{
            return true;
        }        
    }