euler3.lisp

;What is the largest prime factor of the number 600851475143 ?

;algorithm for finding prime factors: divide the number by the first prime number that leaves no remainder (likely 2, 3, or 5), then keep doing that until you get 1. The numbers you divided by are the prime factors.

; is-prime?
;the prime factors of x can never by greater than (sqrt x)
;better to count up than down

;The prime factors of 13195 are 5, 7, 13 and 29.