What is the number of rank with the viewership of 5.96 million?
CREATE TABLE "weekly_ratings" (
  "num" real,
  "episode" text,
  "air_date" text,
  "timeslot_est" text,
  "season" text,
  "rating" text,
  "share" real,
  "18_49" text,
  "viewers_m" text,
  "rank_num" text
);
SELECT COUNT("rank_num") FROM "weekly_ratings" WHERE "viewers_m"='5.96';