How many viewers (millions) were there for rank (week) 20?
CREATE TABLE table_16577 (
    "#" real,
    "Episode" text,
    "Rating" text,
    "Share" real,
    "Rating/Share (18-49)" text,
    "Viewers (millions)" text,
    "Rank (timeslot)" real,
    "Rank (night)" real,
    "Rank (week)" text
)
SELECT COUNT("Viewers (millions)") FROM table_16577 WHERE "Rank (week)" = '20'
Below are sql tables schemas paired with instruction that describes a task. Using valid SQLite, write a response that appropriately completes the request for the provided tables. ### Instruction: How many viewers (millions) were there for rank (week) 20? ### Input: CREATE TABLE table_16577 (
    "#" real,
    "Episode" text,
    "Rating" text,
    "Share" real,
    "Rating/Share (18-49)" text,
    "Viewers (millions)" text,
    "Rank (timeslot)" real,
    "Rank (night)" real,
    "Rank (week)" text
) ### Response: SELECT COUNT("Viewers (millions)") FROM table_16577 WHERE "Rank (week)" = '20'