(50G) Digits sum (50g)

[grsbanks]

(04-12-2020 08:05 PM)Juan14 Wrote:  I was trying factorials and notice that after 6!, if you reduce to a single digit, this is always 9. I know there are guys out there with better knowledge that can explain this.

6! = 1 x 2 x 3 x 4 x 5 x 6 = 1 x 2 x 3 x 4 x 5 x 2 x 3

3 is a factor of 6! twice, which means that it's a multiple of 9, as is the factorial of any integer above 6.

The phenomenon you describe is a property of all multiples of 9.