I'm #8540 on the chess.com puzzle ratings. I was expecting that the top ratings would not go too high, but I was wrong. The top three ratings are all 65540, which for the reasons I give below, I suspect is the highest possible rating.
I find this 65540 number suspicious because the top three ratings are this number. The maximum value that can be stored by a 16-bit number is 65536. If you want to save storage space, why use a 32-bit or a 64-bit number to store ratings when a 16-bit number would do? The 65540 number almost fits. You can make it fit by making the lowest possible rating the number 5. Why would you set a lower limit on the rating? To not accidentally run into a divide by zero problem, which can crash computer code, or other mathematical oddities from having a low or negative number in your equation.