191

This number is a prime.

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(191, 251) is the only pair of 3-digit primes that can be represented as the product of two consecutive primes minus their sum, and to the product of the same primes plus their sum, 13*17 - (13+17) = 191, 13*17 + (13+17) = 251. Note that the concatenations in both orders of the elements of this pair, i.e., 191251 and 251191 are both primes. [Loungrides]

Submitted: 2019-01-31 04:17:31;   Last Modified: 2019-01-31 07:04:33.
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