Its quite easy to determine whether the linux is a 32 or a 64 bit one. Its usually in the kernel name.
To find out. Just type uname -m in the terminal. It gives you something like x86_64 as the output. This tell me that I am running 64 bit kernel.
You can even check a binary file on the system if it is 64 bit. To check this: type file /usr/bin/file in the terminal. The output looks something like the following : /usr/bin/file: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.24, BuildID[sha1]=0x8bdd1d60fb5d744d4ecefcd1f6d0b702f7ba5431, stripped
This indicates that you have 64bit linux operating system.