6173
This number is a prime.
Delete any digit of 6173 and it will remain prime. [Blanchette]
The prime 6173 stays prime if any digit is deleted, and its
sum of digits is the prime in its middle. [Post]
The largest prime formed by concatenating two consecutive double-digit Pythagorean primes. (A Pythagorean prime is a prime number of the form 4n + 1). [Loungrides]
(There are 2 curios for this number that have not yet been approved by an editor.)
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