Largest PRP of the form 10^x-y , (length x).
PRP to base 3,5,7.
PFGW Version 3.7.10.64BIT.20150809.Win_Dev [GWNUM 28.6]
Date of submission : 30 december 2016.
http://www.worldofnumbers.com

The lower borderprp of 10^999999. The upper borderprp is 10^999999+593499.
Together with 10^999999-172473 this produces a rather small gapsize of 765972.
With a gapmerit as low as 0.333 (gapsize/(999999*ln(10)) I was very lucky to find it so quickly.

To be completed...