Monday, October 21, 2013

9998

9998 = 2 x 4999.

9998 is the smallest number n for which the concatenation n, (n + 1), . . . (n + 21) is prime (A052079).

9998 is the smallest even number with digit sum 35 (A069532). It is the largest 4-digit semiprime (A098450).

9998 is a number n such that n and the square of n contain only the "looped" digits 0, 4, 6, 8, and 9 (A107626 and A136956).

9998 divides the sum of the digits of all numbers from 1 to 9998 (A114136).


Source: What's Special About This Number?

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