It's a bit complicated and it depends on what exactly you're measuring. The 68000 CPU has 32-bit registers internally, the address bus is 24-bit, and the data bus is 16.

This is so for A500, but the definitive Amiga is A1200 with 68EC020, AGA and only limited by 24 bit address bus (=16 MB ram). From that on people just installed 030 with MMU and later PPCs if they wanted.