Choose any three by three square of dates on a calendar page...

Can you explain how this card trick works?

Take any whole number between 1 and 999, add the squares of the digits to get a new number. Make some conjectures about what happens in general.

$32 \times 38 = 30 \times 40 + 2 \times 8$ $34 \times 36 = 30 \times 40 + 4 \times 6$ $56 \times 54 = 50 \times 60 + 6 \times 4$ $73 \times77 = 70 \times80 + 3 \times 7$

$32 \times 38 = 30 \times 40 + 2 \times 8$

$34 \times 36 = 30 \times 40 + 4 \times 6$

$56 \times 54 = 50 \times 60 + 6 \times 4$

$73 \times77 = 70 \times80 + 3 \times 7$

And so on?

Verify and generalise if possible.