Owlet puzzle #26
Released Friday, July 31, 2026 UTC
91
the answer for puzzle #26
The five clues
- A two-digit number.
- Looks prime, but isn't.
- The famous 'looks prime, isn't' example.
- 91 = 7 · 13.
- Also the smallest pseudoprime to base 3.
Backstory
Classic trap in number-theory pedagogy: 91 defeats naive primality by eye. 7·13.
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