Name the total number of immunity for cycle number of 13
CREATE TABLE "table1_16976547_2" (
  "cycle_no" text,
  "air_dates" text,
  "reward" text,
  "immunity" text,
  "eliminated" text,
  "vote" text,
  "finish" text
);
SELECT COUNT("immunity") FROM "table1_16976547_2" WHERE "cycle_no"='13';