CREATE TABLE table_16336 ("Season" FLOAT, "Episodes" FLOAT, "Time slot  ( EST ) " CLOB, "Season premiere" CLOB, "Season finale" CLOB, "TV season" CLOB, "Rank" CLOB, "Viewers  ( in millions ) " CLOB)

How many season premiers have a rank of #21?
SELECT "Season premiere" FROM table_16336 WHERE "Rank" = '#21'
SELECT "Season premiere" FROM "table_16336" WHERE "Rank" = '#21'