1723

This number is a prime.

The prime that splits into the two primes, 17 and 23, which are the extremal constants of the magic triangle of Yates using digits 1 through 9:

       1                 7 

     9   6             3   6 

   5       7         5       1 

 2   8   4   3     8   2   4   9

[Beedassy]