CREATE TABLE table_28365 ("No. in series" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" FLOAT)

How many episodes had the production code 66210?
SELECT COUNT("No. in series") FROM table_28365 WHERE "Production code" = '66210'
SELECT COUNT("No. in series") FROM "table_28365" WHERE "Production code" = '66210'