13471...81347 (24-digits)

This number is a prime.

                                                  1347 1123581347 1123581347

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The first emirp formed from the smallest emirp, (13), followed each time from the sum of its two previous digits, i.e., 13, 134, 1347, 134711, 1347112, 134711235813471123, 1347112358134711235, 13471123581347112358, 1347112358134711235813, 13471123581347112358134, 134711235813471123581347. [Loungrides]