2399
This number is a prime.
The third prime of the form 7^n-2, and the largest known number for which 67^n-66^n is prime (as of November 2009). [Hasler]
Albert Einstein and Niels Bohr were born 2399 days apart. [Gaydos]
(There are 3 curios for this number that have not yet been approved by an editor.)
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