Owlet puzzle #13
Released Saturday, July 18, 2026 UTC
12321
the answer for puzzle #13
The five clues
- A five-digit palindrome.
- A five-digit perfect square.
- The square of a three-digit repunit (all 1s).
- It factors as (3·37)² = 9·1369 since 111 = 3·37.
- Row four of a palindromic pyramid: 1, 121, 12321, 1234321, 123454321, ...
Backstory
12321 = 111², a palindromic repunit square. The pattern 1, 121, 12321, 1234321, 123454321 continues cleanly up to 111,111,111² = 12345678987654321, but breaks at 1,111,111,111² where carries interfere.
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