Namw the minimum production code for 16.04 million viewers
CREATE TABLE "table1_14845640_1" (
  "series_num" real,
  "season_num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" real,
  "u_s_viewers_millions" text
);
SELECT MIN("production_code") FROM "table1_14845640_1" WHERE "u_s_viewers_millions"='16.04';