Math Is Fun Forum

Al-Allo

Member

Registered: 2012-08-23

Posts: 324

Factorisation of big numbers...

Hey everyone...I have a little question : How do you factorise big numbers ?

I could just use my calculator but that would be too long... Is there any technique known that I could use ? Take this number : 2016. I must put it in a tree of factors... But there's too many possibilites ..

Thanks !

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Factorisation of big numbers...

Hi;

For a number like 2016 you use trial division. Do you know how?

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Al-Allo

Member

Registered: 2012-08-23

Posts: 324

Re: Factorisation of big numbers...

Mmmh.. An example would be helpful. I already have the prime numbers of 2016. Would that be helpful to find the others ?

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Factorisation of big numbers...

Are you looking for the divisors?

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Al-Allo

Member

Registered: 2012-08-23

Posts: 324

Re: Factorisation of big numbers...

Well, basically, I have the number 2016 and must find its factors in a tree of factors. Could you show me how to proceed ? I don't know if my question is clear^^

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Factorisation of big numbers...

Hi;

What do you mean by a tree of factors. Got a web page with a picture?

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Al-Allo

Member

Registered: 2012-08-23

Posts: 324

Re: Factorisation of big numbers...

I have 2016, the prime numbers at the end, now I need to find the others... I'll be creating you a diagram,

I can't post a link

Last edited by Al-Allo (2012-08-23 08:16:18)

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Factorisation of big numbers...

Seen this page?

http://www.softschools.com/math/factors/factor_tree/

---

In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Al-Allo

Member

Registered: 2012-08-23

Posts: 324

Re: Factorisation of big numbers...

No, but that's what I'Ve been talking about. I have all the prime numbers, but I don't know how to find the others....

Al-Allo

Member

Registered: 2012-08-23

Posts: 324

Re: Factorisation of big numbers...

I know that 2016 = 2 exponent 5 . 3 exponent 2 . 7

bobbym

bumpkin

From: Bumpkinland

Registered: 2009-04-12

Posts: 109,606

Re: Factorisation of big numbers...

Did you try that page? It is self explanatory.

Here is what wolfram does. Okay, where did he go? One second he was here and the next, The Twilight Zone!

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In mathematics, you don't understand things. You just get used to them.
If it ain't broke, fix it until it is.
Always satisfy the Prime Directive of getting the right answer above all else.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,648

Re: Factorisation of big numbers...

hi Al-Allo

2016 is even so divide out a 2.

Keep doing this until you end up with an odd number.

There are some other tricks for finding some factors.  Do you want to know these?

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob