Pluto's radius is 737.6 miles. If a planet has a radius of 500.5 miles, how many people could comfortably live on that planet?

About 42 million, also this is the wrong section. Mathematics is better

How do you propose that life be "supported" on such a tiny planet?

It would have no atmosphere, no biosphere, and no protection from the radiation from space.

The answer is thus zero, unless you made people suffer the indignity of being confined to some "habitat" in which case you might get a few people to somehow exist there for awhile until they all either murdered each other out of space rage or canibalised each other due to starvation.

Cheers!

What does the size of Pluto have to do with this? A planet with a radius of 500.5 miles has an area of 3,147,880 square miles. At 10 people per square mile, that comes to a bit over 30 million people. That's within the range of comfort, if the planet is close to Earth-like.

Depends on what you define as the necessary space to be 'comfortable'... Someone's answer from a rural community in Iowa is going to differ greatly from a person living in downtown Tokyo...

How much space dopes each person require to "live"?

nine

Your question, such as it is, assumes facts not in evidence.

how much surface area does it take for one person to live comfortably?