user: Question: How many episodes have 18.73 million viewers?
Columns: ['No. in series', 'Title', 'Directed by', 'Written by', 'Original air date', 'Prod. No.', 'Viewers (millions)']
Types: ['real', 'text', 'text', 'text', 'text', 'real', 'text']
Sample row: [1.0, '"Identity"', 'James Whitmore, Jr.', 'Shane Brennan', 'September22,2009', 101.0, '18.73']
SQL:

assistant: SELECT COUNT("No. in series") FROM "Table" WHERE "Viewers (millions)" = '18.73';