CREATE TABLE table_73415 ("Season no." FLOAT, "Series no." FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" FLOAT, "U.S. Viewers  ( millions ) " TEXT)

which is the biggest production code?
SELECT MAX("Production code") FROM table_73415
SELECT MAX("Production code") FROM "table_73415"