How to know what is the type of OS: 32-bit or 64-bit?

myserver:/home/oracle:>cd $ORACLE_HOME/bin
myserver:/ora/app/oracle/product/11.2.0.1/bin:>file oracle

oracle: setuid setgid ELF 64-bit LSB executable, AMD x86-64, version 1 (SYSV), for GNU/Linux 2.6.9, dynamically linked (uses shared libs), for GNU/Linux 2.6.9, not stripped