1399
This number is a prime.
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The 65th emirp (1399) has a Collatz trajectory length of
65. [Gaydos]
The smallest prime number whose prime index (222) and sum
of digits (22) together use only one digit. The next two
such primes are 867746501 (44444444 and 44) and 1097774749
(55555555 and 55). [Gaydos]
(There is one curio for this number that has not yet been approved by an editor.)
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