2020 census As of the
2020 census, On Top of the World had a population of 12,668. The median age was 72.5 years. 0.5% of residents were under the age of 18 and 80.8% of residents were 65 years of age or older. For every 100 females there were 82.6 males, and for every 100 females age 18 and over there were 82.4 males age 18 and over. 72.3% of residents lived in urban areas, while 27.7% lived in rural areas. There were 7,203 households in On Top of the World, of which 1.6% had children under the age of 18 living in them. Of all households, 61.1% were married-couple households, 9.8% were households with a male householder and no spouse or partner present, and 25.8% were households with a female householder and no spouse or partner present. About 30.7% of all households were made up of individuals and 27.1% had someone living alone who was 65 years of age or older. There were 7,838 housing units, of which 8.1% were vacant. The homeowner vacancy rate was 2.1% and the rental vacancy rate was 16.6%. ==References==