Unity API not supporting longs (64 bit int)?

Hi all, I would like to use longs in my game, but I'm running into trouble when I try to use it with the Unity API. For instance `Mathf.RoundToLong()` doesn't exist and neither does `PlayerPrefs.SetLong()`. My game requires for me to work with values that exceeds `int.MaxValue`, hence the dilemma. Is there anyone here who can shed some light on this, and maybe point me towards a best practice on working with 64 bit ints in Unity? Thanks!