9967
This number is a prime.
The largest 4-digit left-truncatable prime (emirp). It is
also the largest four-digit deletable emirp. Deleting one
digit at a time, we take a prime at each step, i.e., 967,
97, 7. Note that 967, 97 are also emirps. [Loungrides]
(There is one curio for this number that has not yet been approved by an editor.)
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