Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_name_57 (president VARCHAR, c_span_2009 VARCHAR)

### Question ###
Who is the president when c-span 2009 is 21?

### Accurate SQL ###

SELECT president FROM table_name_57 WHERE c_span_2009 = "21"