51=3.17,80=2 ⁴.5,256=2 ⁸,840=2³.3.5.7,75=3.5²,540=2².3³.5,180=2².3².5,105=3.5.7
51={1,3,17,51},80={1,2,4,5,8,10,16,20,40,80},256={1,2,4,8,16,32,64,128,256},840={1,2,3,5,7,840}
75={1,3,5,15,25,75},540={1,2,3,5,6,9,60,90,108,180,270,540},
180={1,2,3,4,5,6,9,10,12,15,18,20,30,36,45,60,90,180},105={1,3,5,7,15,21,35,105}