26

This number is a composite.

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The only number n < 1000 such that 10^n plus or minus 123456789 are both primes. [Loungrides]

The largest of three successive numbers n, n-1, n-2 such that the product of each of them with its reversal plus 1 is prime, i.e., 26*62+1=1613, 25*52+1=1301, 24*42+1=1009. [Loungrides]