821

This number is a prime.

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2^821+821^3 is the 2nd prime and the largest non-titanic prime of form 2^p+p^3, where p is a prime. The previous such prime is 157. [Loungrides]

The smallest prime in the largest 3-digit prime quadruplet, {821, 823, 827, 829}, whose sums of digits are the terms of the only double-digit quadruplet, {11, 13, 17, 19}. [Loungrides]