661991890601

This number is a prime.

                                                               66 1991890601

+ The smallest invertible prime containing all the invertible digits {0, 1, 6, 8, 9} that can be expressed as T(n) + S(n) + 1, where T(n) is the n-th triangular number and S(n) is the n-th square number, (case n=664325). [Bajpai]

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