175
This number is a composite.
175 = 11 + 72 + 53. Note unity and the first four prime numbers.
The smallest number n greater than 1 such that n^6 + 6 is prime. [Rodrigo]
Smaller in the first pair of Honaker brothers {175, 176}.
The smallest composite number that forms two primes when
its digits are sorted from low to high (157) and from high
to low (751). The next two such composite numbers are 176
and 194. [Gaydos]
(There are 3 curios for this number that have not yet been approved by an editor.)
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