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_11630008_3 ( original_air_date VARCHAR, series_no VARCHAR )

### Question ###
What was the airdate of 21 series number?

### Accurate SQL ###

SELECT original_air_date FROM table_11630008_3 WHERE series_no = 21