Answer:
Factors:
21 : 1, 3, 7, 21
48: 1, 2, 3, 4, 6, 8, 12, 16, 24 and 48.
Multiples :
21 : 21, 42, 63, 84, 105, 126, 147, 168, 189, 210, 231, 252, 273, 294, 315, 336, 357, 378, 399, 420, 441, 462, 483, 504, 525, 546, 567, 588, ...
48 : 48, 96, 144, 192, 240, 288, 336, 384, 432, 480, 528, 576, 624, 672, 720, 768, 816, 864, 912, 960, 1008, 1056, 1104, 1152, 1200, 1248, ...