CREATE TABLE table_31121 ("Series #" FLOAT, "Season #" FLOAT, "Title" TEXT, "Directed by" TEXT, "Written by" TEXT, "Original air date" TEXT, "Production code" TEXT)

What is the series # for the episode titled 'words'?
SELECT MAX("Series #") FROM table_31121 WHERE "Title" = 'Words'
SELECT MAX("Series #") FROM "table_31121" WHERE "Title" = 'Words'