Measuring 35x60cm, 14x24" 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 14x24", you'll need at least 1008 x 1728px and ideally 4200 x 7200px.
If you are looking for a frame with a mat for an 14x24" photo, choose the 18x28" (45x70cm) frame. The mat will have an 14x24" (35x60cm) opening.