Owlet puzzle #18
Released Thursday, July 23, 2026 UTC
1093
the answer for puzzle #18
The five clues
- A four-digit prime.
- One of only two known primes p with 2^(p−1) ≡ 1 (mod p²).
- Called a Wieferich prime.
- 1093 and 3511 are the only Wieferich primes below 6.7 × 10¹⁵.
- First Wieferich prime, found by Meissner in 1913.
Backstory
Wieferich primes are central to Fermat's Last Theorem's first-case criterion. Only two known below quadrillions.
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