The 2016 Greenville, Pennsylvania, population is 650. There are 26 people per square mile (population density). The median age is 33. The US median is 37.4. 55.08% of people in Greenville, Pennsylvania, are married. 5.68% are divorced. The average household size is 2.94 people. 41.95% of people are married, with children. 9.20% have children, but are single.