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_23177573_1 (original_air_date VARCHAR, rank__week_ VARCHAR)
  ### Question:
  What is the original air date of the episode that had a week ranking of 21?
  ### Answer:
  SELECT original_air_date FROM table_23177573_1 WHERE rank__week_ = 21