Talk:Multiplicative digital root

No persistence >11 for n<10^20959 instead of 20585
Benjamin Chaffin checked for the persistence of all numbers <10^20000 that can be composed of primes 2 3 and 7, and found that none of them has persistence >10. That means that there's no number with persistence >11 up to 10^20959, because even if it would consist of only 9s, 9^20959<10^20000. The smallest number (which doesn't have a 5 as a digit) whose product of digits is >10^20000 is 2.69*10^20959-1. I discussed this with Benjamin Chaffin and he agreed with me. But to make sure, I'm posting it here before making an edit. George Albert Lee (talk) 16:19, 30 October 2020 (UTC)


 * Unless this result is mentioned in the relevant literature, and thus with a wp:reliable source, we cannot have it in the article. - DVdm (talk) 22:45, 9 March 2021 (UTC)

digital product
In German, we talk about Querprodukt. The German article links here even though the two aren't equivalent. The equivalent of German Querprodukt is the "digital product". The multiplicative digital root is the recursive or iterative "digital product". I believe it would be good if the English article was extended. Currently, it gives the impression that mathematicians only care about the iterative version of the "digital product".

Querprodukt of 945 = 180, multiplicative digital root AKA iteriertes Querprodukt = 0

Leggewie (talk) 19:25, 24 May 2021 (UTC)