Owlet puzzle #91
Released Sunday, October 4, 2026 UTC
255
the answer for puzzle #91
The five clues
- A three-digit number one less than a power of two.
- A three-digit number whose binary representation is all 1s.
- A number whose three distinct prime factors are all Fermat primes: 3, 5, 17.
- The maximum value of a single color channel in 24-bit RGB.
- Written 0xFF in hexadecimal.
Backstory
255 = 2⁸ − 1 = 3 · 5 · 17 factors into the first three Fermat primes F₀, F₁, F₂. By Gauss's theorem, a regular n-gon is constructible with compass and straightedge exactly when n is a power of two times a product of distinct Fermat primes — so a regular 255-gon is constructible.
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