12345...54321 (823-digits)

This number is a probable-prime (likely to be a prime but we have not (re-)proven it on this site).

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The largest non-titanic palindromic prime of the form 1234567*10^(k + 7) + 7654321 (for k = 809), where k is the number of zeros between 1234567 and 7654321. [Gupta]

Submitted: 2026-01-11 06:17:07; Last Modified: 2026-01-11 15:38:12.