text: Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
  ### Context:
  CREATE TABLE table_18217750_1 (series__number VARCHAR, us_viewers__millions_ VARCHAR)
  ### Question:
  What series number garnered 20.64 million viewers?
  ### Answer:
  SELECT series__number FROM table_18217750_1 WHERE us_viewers__millions_ = "20.64"