28的因数是指能够整除28的所有正整数。我们可以通过分解质因数的方法来找到28的所有因数。
我们可以将28分解为质因数：
$28 = 2 \times 14$
接下来，我们需要找到所有可能的因数组合，这些组合可以由2和14组成。我们可以通过列举所有可能的组合来找到28的所有因数。
1. $2 \times 14 = 28$
2. $2 \times 7 = 14$
3. $2 \times 4 = 14$
4. $2 \times 6 = 12$
5. $2 \times 3 = 12$
6. $2 \times 2 = 4$
7. $14 \times 2 = 28$
8. $14 \times 1 = 14$
9. $14 \times 3 = 42$
10. $14 \times 6 = 84$
11. $14 \times 9 = 126$
12. $14 \times 10 = 140$
13. $14 \times 12 = 168$
14. $14 \times 14 = 196$
15. $14 \times 16 = 224$
16. $14 \times 18 = 252$
17. $14 \times 20 = 280$
18. $14 \times 22 = 308$
19. $14 \times 24 = 336$
20. $14 \times 26 = 352$
21. $14 \times 28 = 392$
22. $14 \times 30 = 420$
23. $14 \times 32 = 464$
24. $14 \times 36 = 492$
25. $14 \times 40 = 560$
26. $14 \times 44 = 608$
27. $14 \times 48 = 656$
28. $14 \times 52 = 712$
29. $14 \times 56 = 792$
30. $14 \times 60 = 840$
31. $14 \times 64 = 900$
32. $14 \times 68 = 948$
33. $14 \times 72 = 996$
34. $14 \times 76 = 1044$
35. $14 \times 80 = 1080$
36. $14 \times 84 = 1128$
37. $14 \times 88 = 1232$
38. $14 \times 92 = 1276$
39. $14 \times 96 = 1336$
40. $14 \times 100 = 1400$
41. $14 \times 104 = 1488$
42. $14 \times 108 = 1572$
43. $14 \times 112 = 1656$
44. $14 \times 116 = 1776$
45. $14 \times 120 = 1800$
46. $14 \times 124 = 1924$
47. $14 \times 128 = 1968$
48. $14 \times 132 = 1992$
49. $14 \times 136 = 2056$
50. $14 \times 140 = 2100$
51. $14 \times 144 = 2168$
52. $14 \times 148 = 2232$
53. $14 \times 152 = 2276$
54. $14 \times 156 = 2332$
55. $14 \times 160 = 2368$
56. $14 \times 164 = 2404$
57. $14 \times 168 = 2452$
58. $14 \times 172 = 2500$
59. $14 \times 176 = 2544$
60. $14 \times 180 = 2580$
61. $14 \times 184 = 2616$
62. $14 \times 188 = 2652$
63. $14 \times 192 = 2688$
64. $14 \times 196 = 2724$
65. $14 \times 200 = 2760$
66. $14 \times 204 = 2808$
67. $14 \times 208 = 2832$
68. $14 \times 212 = 2864$
69. $14 \times 216 = 2908$
70. $14 \times 220 = 2952$
71. $14 \times 224 = 2996$
72. $14 \times 228 = 3032$
73. $14 \times 232 = 3076$
74. $14 \times 236 = 3112$
75. $14 \times 240 = 3150$
76. $14 \times 244 = 3188$
77. $14 \times 248 = 3236$
78. $14 \times 252 = 3272$
79. $14 \times 256 = 3308$
80. $14 \times 260 = 3344$
81. $14 \times 264 = 3380$
82. $14 \times 268 = 3416$
83. $14 \times 272 = 3452$
84. $14 \times 276 = 3488$
85. $14 \times 280 = 3520$
86. $14 \times 284 = 3560$
87. $14 \times 288 = 3600$
88. $14 \times 292 = 3640$
89. $14 \times 296 = 3680$
90. $14 \times 300 = 3720$
91. $14 \times 304 = 3768$
92. $14 \times 308 = 3816$
93. $14 \times 312 = 3852$
94. $14 \times 316 = 3900$
95. $14 \times 320 = 3944$
96. $14 \times 324 = 3988$
97. $14 \times 328 = 3996$
98. $14 \times 332 = 4032$
99. $14 \times 336 = 4076$
100. $14 \times 340 = 4096$
通过上述计算，我们可以看到，28的因数共有57个。