Talk:Composite number

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One of the 500 most frequently viewed mathematics articles.

Misc comments without a heading[edit]

I restored the previous target of the link to 42, to the article Forty-two. I do think that the reference to Hitchhiker's Guide to the Galaxy is an important cultural connotation of the number, but given that this is discussed in the article Forty-two and that article, in its cultural connotations of the number section, gives a link to the Hitchhiker article, it might not be necessary to also mention it in this article on composite numbers, which mainly focuses on the mathematical properties of composite numbers. PrimeFan —Preceding undated comment was added at 18:32, 20 December 2003 (UTC).


But what is this Sphenic number thing? I've never heard of it, and it certainly does not stand the Google test - the only references to i think related Wikipedia. It seems to have been justified by an attempt in trying to proove forty-two is really magic. Pure numerology, in other words. I cannot see any justification that it should stay. -- Egil 10:12, 1 Feb 2004 (UTC)


I won't cry too much if you remove it. But it definitely is verifyiable. Funk & Wagnalls Standard Dictionary International Edition (C)1964 Volume two, page 868, under the heading "number" defines "sphenic number" as "a number product of three unequal prime factors". I have no opinion on the reliability of Funk & Wagnalls, but they definitely seem to know about sphenic numbers, even if google doesn't. -- Jussi-Ville Heiskanen 14:03, Feb 1, 2004 (UTC)

Funny thing is, before Wikipedia, I had never heard of sphenic numbers either. All I can say about them is, that to someone compiling a factorization table by hand (as I have done, even though I could've had a computer do it for me), 3-factor numbers stand out if you're working with numbers below 2310. After you pass 2310, 3-factor numbers don't seem as special as 4-factor numbers, and so on and so forth as you pass each primorial. PrimeFan 17:27, 3 Feb 2004 (UTC)

Several encyclopedias seem to acknowledge the existence of this sphenic number concept - in the first 10 google :
http://www.tiscali.co.uk/reference/dictionaries/difficultwords/data/d0012088.html
http://encyclopedia.thefreedictionary.com/Sphenic%20number
http://www.encyclopedia4u.com/c/composite-number.html
I think we should let this one alive. slord 13:48, 3 Mar 2004 (UTC)

The last two are copied of an old Wikipedia article. Dori | Talk 16:12, Apr 12, 2004 (UTC)

diffence between divisor and prime factors.[edit]

You need to make clear the difference between divisors and prime factors.

For example:

A composite number is a positive integer with three or more divisors.

Compare with

A composite number is a non-prime number with one or more prime factors. —Preceding unsigned comment added by 203.47.84.40 (talk) 04:05, 22 November 2004 (UTC)

Bad Sentence[edit]

"One way to classify composite counting the number of prime factors."

I don't know how this should be worded, but I'm fairly certain that's not a proper English sentence. Since I don't know what it's supposed to say, I can't fix it, but perhaps someone else can. socalifornia 10:21, 8 April 2006 (UTC)

I've added three words which I hope clarify the matter. PrimeFan 22:20, 23 May 2006 (UTC)

"One way to classify composite [numbers is by] counting the number of prime factors."

not understanding[edit]

please i don't understand what numbers are composite,prime or niether can you please explain and type them done 1 to 100? —Preceding unsigned comment added by 211.27.105.4 (talk) 10:51, 27 August 2006 (UTC)

Explain More please[edit]

Hello i'm not really quite understanding it please explain it more and write or type from numbers 1 to 100 wait this sounds to much like the NOT UNDERSTANDING well looks like have something in comman well thanks for listening(READING) bye bye for now —Preceding unsigned comment added by 211.27.105.4 (talk) 10:55, 27 August 2006 (UTC)


I don`t understand the defanition its too complicated explain it and don`t repeat it. I was doing my math homework and my teacher gave me this random homework without explaing it. thanks for reading my messeage. —Preceding unsigned comment added by 69.249.108.23 (talk) 23:42, 10 November 2007 (UTC)

A positive integer n is composite if it can be written as n = x×y, where x and y are integers above 1. For example, 4, 15 and 20 are composite numbers because 4 = 2×2, 15 = 3×5, 20 = 4×5. Is that clear? A prime number is an integer above 1 which is not composite. For example 2, 3 and 5. PrimeHunter 23:56, 10 November 2007 (UTC)

1/1/11 was a freaky day[edit]

I'm wondering how this is possible??? Ok... this is weird.... 1/1/11 was a freaky day.. we all merge on 111.. to prove it.. take the last 2 digits of your year of birth and add them to the age you'll be this year... I did this for everyone in my family and it worked. The ones under the age of 10 when I added the yr and age came to 11 instead of 111. Can you tell me how this is possible? Thanks —Preceding unsigned comment added by 173.21.121.27 (talk) 04:41, 12 January 2011 (UTC)

This actually belongs at Wikipedia:Reference desk/Mathematics but I will give a brief answer. If you are born in year 19yy then you will be 2011-19yy = 111-yy in 2011. And yy + 111-yy = 111. Similarly for 20yy, we get yy + 11-yy = 11. PrimeHunter (talk) 05:00, 12 January 2011 (UTC)