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_19236587_4 ( series_no VARCHAR, uk_viewers__million_ VARCHAR )

### Question ###
What's the series number of the episode seen by 2.43 million viewers in the UK?

### Accurate SQL ###

SELECT series_no FROM table_19236587_4 WHERE uk_viewers__million_ = "2.43"