Project Euler #3

A colleague of mine has suggested solving Project Euler #3 as a challenge. I noticed that his code was working fine but very inefficient. In fact the specification of this task is misleading because it suggests that it is necessary to check if a solution is prime. But it is possible to formulate the solution without checking for primality. Here is my implementation in Kotlin.

fun euler3(n: Long, i: Long = 2): Long =
    if (i >= n) n
    else if (n % i == 0L) euler3(n / i, i)
    else euler3(n, i + 1)

fun main(args: Array<String>)
{
    var numcur = euler3(600851475143)
    print("$numcur")
}

The trick is to quit the loop when i exceeds n.