CREATE TABLE table_67668 ("Number in series" FLOAT, "Number in season" FLOAT, "Title" CLOB, "Directed by" CLOB, "Original air date" CLOB, "Production code" CLOB)

What is the series number that has a production code of 50021 50025?
SELECT MAX("Number in series") FROM table_67668 WHERE "Production code" = '50021–50025'
SELECT MAX("Number in series") FROM "table_67668" WHERE "Production code" = '50021–50025'