The static C++ method QByteArray::number(int n, int base=10) can be called by:

(qt:byte-array.number 37)

which is equivalent to the C++ code QByteArray::number(37);. Or with:

(cxx:number (find-class 'qt:byte-array) 37)

or:

(cxx:number (make-instance 'qt:byte-array) 37)