There are several situations where you need to confirm whether your Linux OS installed is 32bit or 64bit. People normally use uname -a to find it. But the following command will tell you exactly the machine architecture.
getconf utility shall conform to the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax.
[root@localhost ~]# getconf LONG_BIT
My machine is 32bit.