Below is an instruction that describes a task. Write a response that appropriately completes the request.

### Instruction:
What is the episode number of the episode broadcast on 21 September 2001?

### Inputs:
table_name: table, columns: ['Episode Number', 'Broadcast Date', 'Title', 'Written by', 'Viewership (Millions)']

### Response:
SELECT Episode Number FROM table WHERE Broadcast Date = 21 september 2001