Project Euler asks us to find *the largest prime factor of the number 600851475143*.

The following code is fairly straightforward and probably *The Simplest Thing That Could Possibly Work*. It's
called Trial division.

```
def factorise(n):
results = []
check = 2
while check ** 2 <= n:
if not n % check:
n /= check
results.append(check)
else:
check += 1
if n > 1: results.append(n)
return results
```

Note that we don't actually have to worry about prime numbers. The fact that
every positive integer greater than
one has a unique prime factorization and we start with a prime number (2) ensures the following divisables
will be prime numbers too. Also we will only have to check up to the square root of *n* after which the
factor will re-cycle.

Using this and finding the largest prime factor in python is as easy as:

```
max(factorise(600851475143))
```

**Update:** based on some of the feedback I got, I decided to not publish any Project Euler solutions
any more.