CREATE TABLE "table1_22181917_2" (
  "series_num" real,
  "season_num" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" text,
  "u_s_viewers_millions" text
);

Question: How many original airdates did season 20 have?
SQL: SELECT COUNT("original_air_date") FROM "table1_22181917_2" WHERE "season_num"=20;

Question: Who directed the episode that was watched by 6.62 million U.S. viewers?
SQL: SELECT "directed_by" FROM "table1_22181917_2" WHERE "u_s_viewers_millions"='6.62';

Question: What is the production code for the episode with 8.56 million U.S. viewers?
SQL: SELECT "production_code" FROM "table1_22181917_2" WHERE "u_s_viewers_millions"='8.56';

Question: What is the title of the episode that had 9.76 million U.S. viewers?
SQL: SELECT "title" FROM "table1_22181917_2" WHERE "u_s_viewers_millions"='9.76';