Hello! 
The game is indeed 64-bit because it uses more than 4GB of RAM. Software that uses less than 4GB of RAM is typically 32-bit, while software that requires 4GB or more is generally 64-bit.
In this scenario, the operating system version doesn’t affect things much. A 64-bit PC can still run 32-bit games because 64-bit operating systems have built-in compatibility layers (like WOW64) that support 32-bit software. 32-bit software is still widely in use, for example by certain hardware such as printers.
If you encounter an error related to the “bit” version, the solution is to launch the game first. Once you’re at the main menu, press Play in the trainer.
You can find this information by searching the forum, for example: "These cheats were made for the 64-bit version of the game, you are running the 32-bit version" - and vice versa - #2 by Ravenfyre.