In fact, there is a 64-bit version if you look in the right place.
There are various advantages over 32-bit, such as the ability to work with larger files.
Sign into your account then tap the Language and install options link in the Install Information section.
Look to the bottom of the installation window and go for the Additional install options link.
smack the Version menu, pick the Office (64-bit) option, and then click Install.
How to implement the 64-Bit Version of Office 365 for Windows| How-To Geek
