# 73

This number is a prime.

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73 is the only
Sheldon prime, i.e., i) whose binary representation is
palindromic (1001001_{2}) and ii) which belongs to an emirp pair (P

_{n}, P

_{m}) such that subscripts (

*m*,

*n*) = (21, 12) are also reversals of each other and

*n*has a prime decomposition 21 = 3*7 that concatenates back to P

_{m}(Carl Pomerance, Chris Spicer, February 2019). [Beedassy]

Submitted: 2019-04-18 17:18:11; Last Modified: 2019-04-18 18:04:41.

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