Task: Question Understanding
Input (English): Passage: According to the 2010 United States Census, the City and County of Denver contained 600,158 people and 285,797 households. The population density was 3,698 inhabitants per square mile (1,428/km²) including the airport. There were 285,797 housing units at an average density of 1,751 per square mile (676/km²). However, the average density throughout most Denver neighborhoods tends to be higher. Without the 80249 zip code (47.3 sq mi, 8,407 residents) near the airport, the average density increases to around 5,470 per square mile.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.
Question: Which age group had the second largest population?
Output (English): span