Why is 561 the sum of all factors of 400, excluding 400?
The factors of the number 400 are: 1, 2, 4, 5, 8, 10, 16, 20, 25, 40, 50, 80, 100, 200, 400.
If you add them up, you will get the total of 961. Now subtract 400 to get 561
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