question: Which Density per km² is the lowest one that has a Number (map) smaller than 13, and an Area in km² of 11.1?
answer: SELECT MIN(density_per_km²) FROM table_name_21 WHERE number__map_ < 13 AND area_in_km² = 11.1
context: CREATE TABLE table_name_21 (density_per_km² INTEGER, number__map_ VARCHAR, area_in_km² VARCHAR)