10
This number is a composite.
Just showing those entries submitted by 'Gaydos': (Click here to show all)
The 10 prime numbers 1103, 1109, 1117, 1667, 1877, 3001,
3389, 3559, 4001, and 4517 each has the same Collatz
trajectory length as its prime index. There are no more of
these in the first billion primes. Are there any more at
all? [Gaydos]
(There is one curio for this number that has not yet been approved by an editor.)
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