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Euclid's Elements Book IX

Primes, perfect numbers, odd/even. 36 propositions. Depends on Books VII and VIII. IX.20: infinitely many primes. IX.36: perfect numbers.

Propositions 1–12 Squares, cubes, continued proportion Propositions 13–24 Primes, infinitude, third proportional Propositions 25–36 Odd/even, perfect numbers