What number episode was Week 4, Part 1? 
CREATE TABLE table_25391981_20 (episode_number VARCHAR, episode VARCHAR)
SELECT episode_number FROM table_25391981_20 WHERE episode = "Week 4, Part 1"
### Context: CREATE TABLE table_25391981_20 (episode_number VARCHAR, episode VARCHAR) ### Question: What number episode was Week 4, Part 1?  ### Answer: SELECT episode_number FROM table_25391981_20 WHERE episode = "Week 4, Part 1"