The current metro area population of Seoul in 2022 is 9,725,417 (archived) with 5,015,941 women and 4,709,476 men in the city. The density is 15.7 thousand people per square kilometer.
One year in South Korea from September 2021 to September 2022 was an amazing experience.
I miss being able to walk everywhere. Step out of the Dongpyeon apartment and there are 3 bakeries within a 5 minute walk. Pharmacies, doctors, libraries, convenience stores, pet stores, unmanned 24-hour ice cream store, Paris Baguette … it is astonishing how livable the cities in South Korea are.