CREATE TABLE table_170958_2 (official_name VARCHAR, area_km_2 VARCHAR)

What is the official name of the land with an area of 276.84 km2?
SELECT official_name FROM table_170958_2 WHERE area_km_2 = "276.84"
SELECT "official_name" FROM "table_170958_2" WHERE "276.84" = "area_km_2"