Neat. So it's easy to "win" but the challenge comes from placing and disabling towers to balance their kills. And the only punishment for a missed enemy is that it might have added to the smallest tower's killcount.
Got 4572 = 127 * 6^2 after a few tries.
Exploit: you can make your score arbitrarily high by placing and deleting baby towers, since the tower count never goes down and deleted towers don't affect the minimum calculation.