CREATE TABLE table_65351 ("Episode Number" TEXT, "Broadcast Date" TEXT, "Title" TEXT, "Written by" TEXT, "Viewership  ( Millions ) " FLOAT)

What is the episode number of the episode broadcast on 21 September 2001?
SELECT "Episode Number" FROM table_65351 WHERE "Broadcast Date" = '21 september 2001'
SELECT "Episode Number" FROM "table_65351" WHERE "Broadcast Date" = '21 september 2001'