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_17641206_4 (original_airdate VARCHAR, viewership VARCHAR)
### Question:
What was the first airdate with a viewership of 4.77 million?
### Answer:
SELECT original_airdate FROM table_17641206_4 WHERE viewership = "4.77 million"