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_25246990_5 ( original_us_air_date VARCHAR, us_viewers__millions_ VARCHAR )

### Question ###
How many different original U.S. air dates appear where the U.S. viewers were 2.5 million?

### Accurate SQL ###

SELECT COUNT(original_us_air_date) FROM table_25246990_5 WHERE us_viewers__millions_ = "2.5"