[American Infidel]

A fun one:

Most may already know that the digits of any number that is evenly divisible by 9 will add up to 9 such as: 9,18,27,36..108 etc.

However if you take ANY number that is two digits or more, add the numbers together, subtract that sum from the original number, that result will also add up to 9 when you break it down. For example:

3275

3+2+7+5 = 17

3275 - 17 = 3258

3+2+5+8 = 18

1+8 = 9

This works with ANY number that is 2 digits or more. I am sure there is a perfectly logical mathematical rationale for this that is beyond my education level, but it is pretty cool how everything seems to come back to the number 9.

[Chickensoup]

I didn’t know that. Some sort of principle must be working there.

[Fledermaus]

Old accountant tool to find transpositions.

[kosciusko51]

The is a perfectly logical mathematical rationale for this.

10 ÷ 9 leaves a remainder of 1, so 50 ÷9 leaves a remainder of 5.

100 ÷ 9 remainder is 1, etc.

[Albion Wilde]

it is pretty cool how everything seems to come back to the number 9.

The Beatles thought so, too. One of their only published avant-garde works:

Revolution 9