Owlet puzzle #69
Released Saturday, September 12, 2026 UTC
7
the answer for puzzle #69
The five clues
- A one-digit prime with a lucky reputation.
- A Mersenne prime — one less than a power of two.
- The smallest prime greater than five.
- The number of days in a week.
- The smallest number that cannot be constructed as a regular polygon with compass and straightedge.
Backstory
A regular heptagon (7 sides) cannot be constructed with compass and straightedge — Gauss proved it, since 7 is not a Fermat prime. The 17-gon can, and Gauss famously requested a 17-gon on his tombstone. Seven is also the smallest prime whose reciprocal repeats with the maximum period 6 in base 10.
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