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_name_57 (president VARCHAR, c_span_2009 VARCHAR)
### Question:
Who is the president when c-span 2009 is 21?
### Answer:
SELECT president FROM table_name_57 WHERE c_span_2009 = "21"