Yes, you can!
In fact, you can have it on multiple devices: it can be your computer (no matter if it is Windows, MacOS or Linux based computer), or/and Android tablet. But in order to run Viber on your computer or/and Android tablet, you must first have the application installed and registered to a mobile device.
What does it mean? I means that, while installing Viber on additional device, you’ll be asked to enter the code which you’ll get in SMS on the registered mobile device. All of your installed Viber applications on different platforms are associated with the same mobile number and therefore are synced. That also means that you can not have the same account on different mobile device. At this stage, one Viber number can be assigned with only one mobile device simultaneously. When you try registering to Viber with the same number on a second mobile device, the first device immediately deactivates, and its data (message history, Recents, etc.) is deleted. What you can do, however, is to register your second mobile device with a different number: your home number, an old cellphone number, family’s or friends… The only requirement is that you are able to receive an activation SMS on it.
In case of 2 SIM cards on same mobile device please check: How do I install Viber.