SELECT MAX("Production code") FROM table_26319 WHERE "U.S. viewers (millions)" = '16.10'
What the production code for the episode with 16.10 U.S. viewers?
CREATE TABLE table_26319 (
    "No. in series" real,
    "Title" text,
    "Directed by" text,
    "Written by" text,
    "Original air date" text,
    "Production code" real,
    "U.S. viewers (millions)" text
)