How do you tell if you're running on 32-bit or 64-bit hardware?
While the command uname -a will show wether you are using a 32-bit or 64-bit Operating System (as well as possibly looking at /etc/*release), it won't tell you if your hardware is actually 64-bit or not.
Instead, look at /proc/cpuinfo by running cat /proc/cpuinfo and look for lm in the flags section. If this flag exists, it's a 64-bit architecture for your CPU.
An easy way to do this is to type the following command. A blank line will be returned if it's false (i.e., not 64-bit) or it will print one or more lines (depending on the number of CPUs and Cores in your computer).
$ cat /proc/cpuinfo | grep lm