Hi guys,
apparently you can see week numbers in the Android app by default. You can select day, week or month view and while in weekview, it will be shown.
For Apple users: you can only select day or month view. But by tilting the iPhone the calendar will automatically switch to week view. There you might see the week number. That depends on whether you activated that setting which by default is turned off.
I don't know if the Android app had this feature all along or if it's new since some build.
But anyway: both platforms can show you weeknumbers
HTH
Jeroen