In the decimal system, if the sum of digits of a number is a multiple of 9, then the number must be a multiple of 9. For example: 2+9+ 1+6= 18=9×2. 29 16/9=324。 The multiplication of 9 is wonderfully related, such as 9× 9 = 8199× 99 = 9801999× 999 = 998001and so on. In digital sum theory, people use this property to develop a set of so-called discard nine algorithms. The difference of any array with the same number, the same digits and different arrangements can be divided by 9, for example, 321-123 =198198/9 = 22; 9876-6897=2979 2979/9=33 1。 Power supply number192 865 438+0 3729 46 561559 049 653174 782 969 843 046 7219387 420. 489 10 3,486,784,40 1 1 1 3 1,38 1,059,609 12 282,429,536,48 1 13 2,54 1, 865,828, 329 14 22,876,792,454,96 1 15 205,89 1, 132,094,649 16 1,853,020, 188,85 1,84 1 ……