Perfect numbers like perfect men are very rare.

The remark draws an analogy between the mathematical notion of “perfect numbers” (a rare class of integers with special divisor properties) and the moral or philosophical ideal of a “perfect man.” Its point is less about number theory than about human aspiration: ideals can be precisely defined, but instances that fully meet the definition are exceptional. Read this way, the line functions as a skeptical or chastening aside—suggesting that both in mathematics and in ethics, one should not expect perfection to be common, and that rarity itself is part of what makes “perfection” meaningful as a standard.