689

This number is a composite.

+ The smallest strobogrammatic brilliant number. If we delete the central digit, then we obtain the smallest strobogrammatic semiprime. [Capelle]

+ The only strobogrammatic brilliant number that can be represented as sum of two powers with distinct prime-digits as bases and distinct composite digits as exponents, i.e., 2^6+5^4 = 689 = 13 × 53. [Loungrides]

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