Economists' favorite number is one: one person/firm/country/good. Their second favorite number is two: one person/firm/country/good and a composite representing all the rest. Economists don't like numbers greater than two so much when making models because with three or more, complex interaction effects can occur.  That to me is the whole point, though. The world is complex, and reducing it to a single ("representative") agent or to one versus the rest of the world often produces misleading results by neglecting differences that are vitally important economically or politically. Money, for instance, requires the existence of at least three goods in principle, and many more in practice. Hence I was gratified to come across this passage:

I am speaking of the claim that it is best for the city to be entirely one to the greatest possible degree, for Socrates adopts that hypothesis [in Plato's Republic]. And yet it is evident that by advancing and becoming more of a one it will not be a city. For a city is by nature a certain kind of multiplicity; by becoming more of a one it would turn from a city into a household and from a household into a human being.

— Aristotle, Politics, Book II, chapter 4, Bekker page 1261B about lines 16-20, translated by Joe Sachs (Newburyport, Massachusetts: Focus Publishing, 2012)