Mathematics is not only a logical problem, but also something to remember, such as multiplication formula table, square table, many constants and so on.

First look at 729. Add up all the figures to 7+2+9= 18. If the result is greater than 10, repeat the process of 1+8=9. If the final result is 9, the number is a multiple of 9: 729/9=8 1. Now you can see: 729.

If you don't understand, another method is to directly divide 729 by 3: 729/3 = 243, 243/3 = 8 1, 8 1/3 = 27, 27/3 = 9, 9/3 = 3, so 729 is equal to the sixth power of 3, which is also equal to.