Owlet puzzle #10
Released Wednesday, July 15, 2026 UTC
220
the answer for puzzle #10
The five clues
- A three-digit multiple of twenty.
- It has a paired 'friend' whose divisors sum to it.
- Known to the Pythagoreans as one half of the earliest amicable pair.
- The smaller member of the smallest amicable pair (220, 284).
- Its aliquot sum is 284 — its proper divisors add up to that number.
Backstory
The lesser of the first amicable pair (220, 284): σ(220) − 220 = 284 and σ(284) − 284 = 220. Known to the Pythagoreans; Fermat added (17296, 18416) in 1636, and Descartes independently found (9363584, 9437056).
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