Find all the prime factors of $1000027$
Find all the prime factors of $1,000,027$.
I got all the factors by testing every number from $1$ to $103$:P, but when I try to do it using algebra, I get stuck.
My work:
$$1000027$$
$$=(100+3)(100^2-3\cdot100+3^2)$$
How do I simplify further?
Go with the sum of cubes and factor out the $103$ thing (which you already did), then notice that $$100^2-3\cdot100+3^2= \\ =100^2+2\cdot3\cdot100+3^2-3\cdot3\cdot100=\\ =(100+3)^2-30^2$$ then factor it as a difference of squares. Then you'll only have to factor $133=7\cdot19$ by hand and verify that everything else is prime.
Come to think of it, this might be an example of Aurifeuillean factorization. Pretty much everybody knows that $x^4+4=(x^2+2x+2)(x^2-2x+2)$. Now we used (rediscovered, if you'd like) a more complicated thing of the same sort: $$x^6+27=(x^2+3)(x^2+3x+3)(x^2-3x+3)$$
I think that the only important step is the first one.
If you want to find the prime factors of $73\times 103$ it is going to be tough, because you have to try all primes up to $73$.
On the other hand, once you find the factor $103$, factoring $7\times 19\times 79$ is easy by brute force, because the factors $7$ and $19$ are found really fast, and then proving that $79$ is prime is done quickly also.