identify if QVariant is String or Int

I will do a method that write data on modbus. I need that QVariant return if is String or Int.

My var.: QVariant dataToWrite

Exist a method that return dataToWrite content is String or Integer? In c# I did how this solution: How do I identify if a string is a number?

I saw documentation on this link: http://doc.qt.io/qt-5/qvariant.html But in qt i didn't find solutions.

Thanks