CREATE TABLE table_26961951_6 (no_in_series INT, us_viewers__million_ VARCHAR)

Which episode number had a viewership of 0.56 million?
SELECT MAX(no_in_series) FROM table_26961951_6 WHERE us_viewers__million_ = "0.56"
SELECT MAX("no_in_series") FROM "table_26961951_6" WHERE "0.56" = "us_viewers__million_"