user: Question: What episode number had US viewership of 4.87 million?
Columns: ['№', '#', 'Title', 'Directed by', 'Written by', 'Original air date', 'Production code', 'U.S. viewers (million)']
Types: ['real', 'real', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: [44.0, 1.0, '" Olivia "', 'Joe Chappelle', 'J. H. Wyman & Jeff Pinkner', 'September23,2010', '3X6101', '5.83']
SQL:

assistant: SELECT "№" FROM "Table" WHERE "U.S. viewers (million)" = '4.87';