12345...61717 (27-digits)

This number is a prime.

1234567 8910111213 1415161717

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A prime formed by concatenating the numbers 1 to 18, then subtracting 1. This is the largest known such prime as of 15 Aug 2025. [Gupta]

Submitted: 2025-08-15 11:17:12; Last Modified: 2025-08-15 11:27:49.