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_203_784 ( id number, "no. in\nseries" number, "no. in\nseason" number, "performer" text, "appearance" text, "air date" text )

### Question ###
how many performers appeared on the air date 21 january 2011 ?

### Accurate SQL ###

SELECT COUNT("performer") FROM table_203_784 WHERE "air date" = '21 january 2011'