Measuring 22x40cm, 9x16" is a common size for photo prints, art work and posters. The standard way to measure a print is by measuring width by height.
To get the best print result for 9x16", you'll need at least 648 x 1152px and ideally 2700 x 4800px.
If you are looking for a frame with a mat for an 9x16" photo, choose the 13x20" (32x48cm) frame. The mat will have an 9x16" (22x40cm) opening.