666666

+ The only six-digit repdigit such that the sum of itself and all truncations of itself plus one is an emirp. [Bajpai]

+ The only 6-digit repdigit number such that the product of itself and all truncations of itself plus one is prime, i.e., 666666*66666*6666*666*66*6+1 and at the same time the concatenation of all the above digits, i.e., 6666666666666666666661, is also prime. [Loungrides]

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