how to find a number is made up of multiplication of which nos?

Question

for example 5764328 is got by multiplication of x*y*z*a*b e.t.c how could u tell by which numbers is it achieved without dividing or taking help of calculators or computer or even a pencil , just see a no & tell that this no is made by multiplication of x & y &z e.t.c guess i know the answer also i have got many tricks to find it out without even taking a pencil or pen or any calcuating machine

Answer 1

This is easy for smaller numbers, but as the number gets larger the problem gets difficult in a hurry. In fact one type of "strong encryption" is based on the fact that when a number gets to be several hundred digits long, all the computing power in the world won't factorize it. (The RSA code - used by PGP et.al.)

Answer 2

Ther are MANY tricks, including lots related to the MODULO function ("clock" numbers). However fundamentally there is NO DIRECT WAY to factor a given number. Very large numbers cannot be factored (in the long run) without plain trial and error. THis, as a matter of fact, is the reason why modern cryptography (as used in computer communication) is so sound and effective: in essence the translation "key" to a cipher is a horrendously large number, and it is presumed that it would take far too long for you to calculate its factors. (The factors themselves are the REAL "key"). The class of mathematical problems that can only (so far as we know) be solved by trial and error is called "NP complete", which you can read about with a little searching on the web.

Answer 3

I can't tell just by looking at it.. so.. not being gifted that way.. I have to break it down into factors.. normally, if it is even, I divide by 2 first...
2 * 2882164.. still even
2*2* 1441082 still even
2*2*2*720541 now odd...not ending in 5 so not divisible by 5, digit sum of 720541 is 1.. so not divisible by 9 so check 3 .. 24018r1 no..so check 7.. 102934r3 no so check a list of prime numbers to see if 720541 is prime.. check < I checked 720500 to 720550> http://www.rsok.com/~jrm/printprimes.html and this was not in there so it is not prime...so just keep working your way up the prime number list cheating.. i use my calculator.. and get.. 317 * 2273

so your answer is:
2*2*2*317*2273 <*GriN*>

Answer 4

Easy, 1 * 5764328 = 5763428 works for every number even prime numbers.