19

This number is a prime.

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"19" has never been found in the sequence 2, 23, 235, 2357, 12357, 3, ... . (The content editor of "Prime Curios!" offers $19 to the first to find it.)

Submitted: 2025-11-13 15:00:14; Last Modified: 2026-07-13 20:03:29.