Bluestacks, the project bringing Android to desktop and currently on Windows and Mac has Whatsapp. Could try that.

Sort of related, is there any way to get an activation code without a proper mobile number? I know I should try Twilio and other options first, but I did just try Google Voice and it didn't seem to work. I could be wrong though. So might as well try asking.

Thanks! I've activated my number. However I cannot get the IMEI. It has very poor UI. There is no UI for dialing.

Edit: there is apps to download which shows your IMEI.

BlueStacks developer here: Glad it worked for you :)