Age distribution was 22.0% under the age of 18, 10.7% from 18 to 24, 36.1% from 25 to 44, 20.0% from 45 to 64, and 11.3% who were 65 years of age or older. The median age is 33 years. Overall there were 102.1 males for every 100 females, but in 2015 for the category of never-married ages 25 to 34, there were 121.4 males for every 100 females. Due to a skewed sex ratio wherein single men outnumber single women, some protologists have nicknamed the city as Menver.
Denver is in the center of the Front Range Urban Corridor, between the Rocky Mountains to the west and the High Plains to the east. Denver's topography consists of plains in the city center with hilly areas to the north, west and south. According to the United States Census Bureau the city has a total area of 155 square miles (401 km2), of which 153 square miles (396 km2) is land and 1.6 square miles (4.1 km2) (1.1%) is water. The City and County of Denver is surrounded by only three other counties: Adams County to the north and east, Arapahoe County to the south and east, and Jefferson County to the west.