The above image shows the completed grid, first with numbers assigned and second with pentomino letters labeled. The product of the empty regions is 1620. Quick note that 1296 was the most common incorrect answer submitted, which is what you get if you slide the I pentomino composed of 5’s to the left one square. Alas, that arrangement leaves the filled squares in two disconnected regions so is not a valid arrangement.

Congrats to this month’s solvers!