19999

This number is a composite.

+ 19999 is a semiprime with the remarkable property that 19999^404 begins with the digits 404, 19999^414 begins with the digits 414, 19999^424 with 424, 19999^434 with 434, 19999^444 with 444, and 19999^454 with 454. [Hartley]

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