Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_25668962_1 ( no_in_series INTEGER, us_viewers__million_ VARCHAR )

### Question ###
What episode number in the series was viewed by 13.66 million people in the U.S.?

### Accurate SQL ###

SELECT MAX(no_in_series) FROM table_25668962_1 WHERE us_viewers__million_ = "13.66"