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

### Instruction:
How many episodes have 18.73 million viewers?

### Inputs:
table_name: table, columns: ['No. in series', 'Title', 'Directed by', 'Written by', 'Original air date', 'Prod. No.', 'Viewers (millions)']

### Response:
SELECT COUNT No. in series FROM table WHERE Viewers (millions) = 18.73