Talk:Persistence of a number

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
WikiProject Mathematics (Rated Start-class, Low-priority)
WikiProject Mathematics
This article is within the scope of WikiProject Mathematics, a collaborative effort to improve the coverage of Mathematics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
Mathematics rating:
Start Class
Low Priority
 Field:  Number theory


I'm dubious about the words 'simplest form,' since I don't see how we can call 9 the 'simplest form' of 2781. How is 9 a form of 2781?! Usually when we say "simplest form" (reducing fractions, simplifying algebraic expressions, etc.), we're making only a cosmetic change. Changing 2781 into 9 is more than cosmetic. Doops 16:49, 30 Apr 2004 (UTC)

Presumably the term persistence can be used in other ways, other than referring to digital roots by addition or multiplication. Let me try and fix that sentence. Dysprosia 00:40, 1 May 2004 (UTC)
Of course, the wording simplest form is too fuzzy; instead, it is a fixed point of the operation, i.e. a number on which the operation yields the same number again. I have majorly rewritten the article to account for that. By the way, I don't think the term persistence of a number is used in mathematics for anything but the additive and multiplicative persistence. Therefore, I think we can get rid of the overly abstract first sentence and just say what additive and multiplicative persistence is. Comments? --Yogi de 22:17, 5 Jun 2005 (UTC)

Reading this article is a good example of the need for some way of easily reading large digits if one wants to quickly know the size. I prefer commas, 234,234,234,234.0234, but I don't mind spaces 234 234 234 234 023 4, as either is better than 234234234234.0234. Without such a visual aid, it is annoying and I suppose stubborn persistence not to make a decision on whether or not to use commas or spaces, use ISO or not. —Preceding unsigned comment added by (talk) 03:05, 31 July 2009 (UTC)

Are any results known for non-decimal bases? Double sharp (talk) 10:19, 20 June 2014 (UTC)

Clarifying the simple algorithm for calculating the persistence of a number.[edit]

In the article, it says "By cleverly using the specific properties of numbers in this sequence, the above terms can be calculated in a fraction of a second.". Is it possible if a citation to this algorithm, or a brief explanation could be provided? I think that would provide a clearer understanding of the mathematics to the reader. — Preceding unsigned comment added by Svdsps (talkcontribs) 20:55, 23 January 2017 (UTC)

I agree that this sentence was not very helpful. I replaced it by a more precise description of the properties that help speed the search. —David Eppstein (talk) 23:07, 23 January 2017 (UTC)
Oh yee of uncertain faith, to wit: function multiplicativePersistence(a,b){for(var d=0,f=a.toString(b);console.log(d+":"+f),!(1>=f.length);)f=[...f].map(h=>parseInt(h,b)).reduce((h,i)=>h*i,1).toString(b),d++;return d} multiplicativePersistence(277777788888899,10); WurmWoodeT 14:34, 29 March 2019 (UTC)