Converting double to string creates inaccuracy

I have this interresting problem, it occured just here, in other situations, the script works fine.

I am counting length from coordinates:

Command: (setq bod1 ppo_bod1)
(-0.821965 -1.7232 0.0)

Command: (setq bod2 ppo_bod2)
(25.428 13.1268 0.0)

Command: !mfac
0.025

Command: (setq x (atoi (rtos(/ (abs (- (car bod2) (car bod1))) mfac))))
1050

Command: (setq y (atoi (rtos(/ (abs (- (cadr bod2) (cadr bod1))) mfac))))
593

Command: (- (cadr bod2) (cadr bod1))
14.85

Command: (/ (abs (- (cadr bod2) (cadr bod1))) mfac)
594.0

Command: (rtos(/ (abs (- (cadr bod2) (cadr bod1))) mfac))
"593.99999998"

Command: (atoi (rtos(/ (abs (- (cadr bod2) (cadr bod1))) mfac)))
593

As you can see, the conversion from 594.0 (real) to string causes an inaccuracy, which is strange, because the length really is 594.0