What was the number of US Viewers in the episode directed by Steve Shill and having a production code of E2102?
CREATE TABLE "table1_21781578_2" (
  "season_no" real,
  "title" text,
  "directed_by" text,
  "written_by" text,
  "original_air_date" text,
  "production_code" text,
  "u_s_viewers_millions" text
);
SELECT "u_s_viewers_millions" FROM "table1_21781578_2" WHERE "directed_by"='Steve Shill' AND "production_code"='E2102';