This number is a composite.

                                                                2 1757820799

+ 21757820799 = 3*11*13*683*74257 = 3111368374257/143 is the second number which divides the concatenation of its prime factors. The first such number is 28749. The third is unknown as of 2009 but 119 large solutions are known based on a method using factorizations of 10^b+1. [Andersen]

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