Factor This 10-Digit Number

The number 1003003001 1003003001 is the product of N N (not necessarily distinct) primes. What is the value of N N ?

Details and assumptions:

  • The number 32 = 2 × 2 × 2 × 2 × 2 32 = 2\times 2 \times 2 \times 2 \times 2 is the product of 5 primes.


The answer is 9.

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20 solutions

Linus Setiabrata
Dec 1, 2013

Note that ( 1 0 x + 1 ) 3 = 1 0 3 x + 3 × 1 0 2 x + 3 × 1 0 x + 1 (10^{x}+1)^{3}=10^{3x} + 3 \times 10^{2x} + 3 \times 10^{x} + 1

For x=1, 1 1 3 = 1331 11^{3}=1331

For x=2, 10 1 3 = 1030301 101^{3}=1030301

And for x=3, 100 1 3 = 1003003001 1001^{3}=1003003001

By quick check of factoring rules, we see 1001 is divisible by 7, 11, and therefore 13, so 1003003001 = 7 3 × 1 1 3 × 1 3 3 1003003001=7^{3} \times 11^{3} \times 13^{3} which gives us 9 \boxed{9} prime factors.

Great explanation of how to easily find the prime factors in this case.

Calvin Lin Staff - 7 years, 6 months ago

Beautiful solution!

Kabelo Moiloa - 7 years, 6 months ago

Awesome

Krishna Gundu - 7 years, 6 months ago

awesome

Eshan Vijayant - 7 years, 6 months ago

nice

sonu sekar - 7 years, 6 months ago

what a thinking!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Shantanu Raut - 7 years, 6 months ago

Awesome

Anwar Petrus Naiborhu - 7 years, 6 months ago

brilliant

Anurag Joshi - 7 years, 6 months ago

wow :)

Kishore Kumar - 7 years, 6 months ago

great answer

saranya bandi - 7 years, 6 months ago

What a nice approach!

Theodorus Jonathan - 7 years, 6 months ago

Superb concentration on numbers......

Vinay Durgam - 7 years, 6 months ago

Hats Off..:)

Vikash Kumar - 7 years, 6 months ago

Great !!!!!!!

Devesh Rai - 7 years, 5 months ago

It is awesome & easy to understand & can also be used for such other problems.

Muneeb Ahmad - 7 years, 4 months ago
Arkan Megraoui
Dec 4, 2013

We notice the symmetry in the number. 1,3,3,1. This should remind us of Pascal's triangle. In particular, the expansion ( x + 1 ) 3 = x 3 + 3 x 2 + 3 x + 1 (x+1)^3=x^3+3x^2+3x+1 . Letting x = 1 0 3 x=10^3 we get ( 1 0 3 + 1 ) 3 = 1 0 9 + 3 1 0 6 + 3 1 0 3 + 1 = 1003003001 (10^3+1)^3=10^9+3\cdot 10^6+3\cdot 10^3+1=1003003001 , which is our number. So we want the number of prime divisors of ( 1 0 3 + 1 ) 3 = ( 1001 ) 3 = ( 7 11 13 ) 3 = 7 3 1 1 3 1 3 3 (10^3+1)^3=(1001)^3=(7\cdot 11\cdot 13)^3=7^3\cdot 11^3\cdot 13^3 , so the answer is 3 + 3 + 3 = 9 3+3+3=\boxed{9} .

Remark: 1001=7 11 13 is a very common factorization in the math competition world - strap it to your tool belt!

Wonderful

Ujjayanta Bhaumik - 7 years, 6 months ago

Remark should say "1001 = 7 * 11 * 13".

Arkan Megraoui - 7 years, 6 months ago

Outstanding

Pioneer Sonnet - 7 years, 6 months ago

superb ....

Prem Arya - 7 years, 6 months ago

awesome.

saurabh anand - 7 years, 6 months ago
Lukman Nulhakim
Dec 1, 2013

1003003001 = 7^3 * 11^3 * 13^3 ,so 1003003001 has a 3 + 3 + 3 = 9 product

JOKES

Ujjayanta Bhaumik - 7 years, 6 months ago
Bob Bob
Dec 21, 2013

1003003001 1003003001 is 100 1 3 1001^3 because ( 1000 + 1 ) 3 = 100 0 3 + 3 100 0 2 + 3 1000 + 1 (1000+1)^3 = 1000^3+3\cdot1000^2+3\cdot1000+1 1001 = 7 11 13 1001 = 7\cdot11\cdot13 , 3 primes. When you cube it, you multiply these three times, to get 9 primes.

CALCULATOR JINDA BAD

BRILLIANT SHIVAM - 7 years, 3 months ago

1003003001 = 7x7x7x13x13x13x11x11X11 , 9 primes

Shah Moshahed Ullah Quaderi - 7 years, 2 months ago
Sunil Pradhan
Dec 1, 2013

1003003001= (1001)^3 = (7 × 11 × 13)^3 = 7^3 × 11^3 × 13^3

total primes = 3 + 3 + 3 = 9

Arnav Shringi
Dec 2, 2013

Prime factorisation of 1003003001 is

                   7 X 7 X 7 X 11 X 11 X 11 X 13 X 13 X 13

They are 9.

The number 1003003001=7x7x7x11x11x11x13x13x13 is the product of 9 primes.

1 003 003 001 = 1001 x 1001 x 1001 = (7 x 11 x 13)^3 3 x 3 = 9

From the binomial theorem (or Pascal's triangle) we see that 1003003001 is a perfect cube

∛(1003003001) = 1001 = 7•11•13, which has 3 prime factors, so N = 3•3 = 9

Muskan Dawar
Dec 3, 2013

when we do prime factorization of 1003003001 we get, 11^3 * 13^3 * 7^3 so there are total 9 prime factors....:)

Jay Reiter
Jun 8, 2016

A simple method for ESTIMATING the number, n, of prime factors for a large number N can be used:

n ~ ln ( ln ( N ) ) ^ 2

For 1003003001, ln ( ln ( 1003003001 ) ) ^ 2 = 9.1894... ~ 9

This estimation becomes more and more accurate with greater numbers

Yatin Jaiswal
Dec 11, 2013

Very Simple it's 7 x 7 x 7 x 11 x 11 x 11 x 13 x 13 x 13 =1003003001 All are prime and total are 9!!

Kuljot Shah Singh
Dec 11, 2013

Start by dividing with prime no. As u will go u will see it will result in.. 7x7x7x11x11x11x13x13x13

Tanay Kocharekar
Dec 10, 2013

1003003001 = 1001^3 1001= 1 7 11*13 total 3 prime numbers, 3 times. That makes it 9

Ivan Koswara
Dec 10, 2013

Complete proof :

Note that 1003003001 = 7 3 1 1 3 1 3 3 1003003001 = 7^3 \cdot 11^3 \cdot 13^3 and 7 , 11 , 13 7,11,13 are primes, so it is the product of N = 3 + 3 + 3 = 9 N = 3+3+3 = \boxed{9} primes.

Motivation :

1003003001 1003003001 looks similar to 1331 = 1 1 3 1331 = 11^3 . Indeed, if we remember the binomial expansion of ( x + 1 ) 3 = x 3 + 3 x 2 + 3 x + 1 (x+1)^3 = x^3 + 3x^2 + 3x + 1 , we can see that 1 1 3 = 1331 11^3 = 1331 can be obtained from the binomial expansion by x = 11 x=11 . In this case, 1003003001 1003003001 can be obtained from the binomial expansion by x = 1000 x=1000 , so 1003003001 = 100 1 3 1003003001 = 1001^3 . Finally, 1001 = 7 11 13 1001 = 7 \cdot 11 \cdot 13 is a well known factorization.

"we can see that 1 1 3 = 1331 11^3 = 1331 can be obtained from the binomial expansion by x = 11 x=11 "

I realize that typo >_< Should be x = 10 x = 10 .

Ivan Koswara - 7 years, 6 months ago
Tarun V Kumar
Dec 8, 2013

WE NEED TO PRIME FACTORIZE THE GIVEN NUMBER. 1003003001= 7 x 7 x 7 x 13 x 13 x 13 x 11x 11 x 11

Charles Lunas
Dec 7, 2013

Test first for the factors by dividing 1003003001 to all possible prime numbers, starting from 1, 2, 3, 5, 7, 11, 13, so on.. and check which will result a whole number.

Then you'll notice that it divides by 7, 11, and 13, resulting into whole number.

Prime factorization = 7 11 13 = 1001 7*11*13 = 1001

Next, divide the given number to its prime factorization:

1003003001 / 1001 = 1002001 1003003001/1001 = 1002001

Repeating the process by dividing it to its proper prime factorization... 1002001 / 1001 = 1001 1002001/1001 = 1001

then 1001 / 1001 = 1 1001/1001 = 1

Therefore: 1003003001 = 7 3 × 1 1 3 × 1 3 3 1003003001 = 7^3 \times 11^3 \times 13^3 and N = 3 + 3 + 3 = 9 N = 3 + 3 + 3 = 9

Anubhav Sharma
Dec 6, 2013

you have to prime factorise it. it is hard i know but. you can use a calculator if you want. But what is the divisor ? First it's 7 Like this carry on till you have got a less number. Then since you have three tries you can guess if you like it. But it's luck The correct answer is 9.

Samuel Queen
Dec 5, 2013

1003003001 1003003001 is clearly not even, nor is it divisible by 3 3 because its digit sum is not and it isn't divisible by 5 5 . Now 7 3 × 2924207 = 1003003001 7^{3} \times 2924207= 1003003001 and 7 7 doesn't divide 2924207 2924207 , but continuing dividing by the next prime as many times as possible we find 1003003001 = 7 3 × 1 1 3 × 1 3 3 1003003001 = 7^{3} \times 11^{3} \times 13^{3} which is nine primes.

Pouya Hamadanian
Dec 5, 2013

1003003001=1000^3+3 1000^2 1^2+3 1000^1 1^2+1^3=(1000+1)^3 1001=13 11 7 ==> 1003003001=13^3 11^3 7^3

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