341
This number is a composite.
341 is the smallest pseudoprime to base two. In 1819, French mathematician Pierre Frédéric Sarrus observed that 341 divides 2³⁴¹-2.
The smallest member of the series n(n + 1 ) - 1 which, if composite, is not the product of two smaller primes in the series of the form 10k - 1 or 10k + 1. [McNamara]
(There are 4 curios for this number that have not yet been approved by an editor.)
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