Some abilities sound a bit overpowered in the calculator class,like:prime number of 5.

I don-t know if its what i think is,then i could use 5 potions at a time?

This class sounds like a headache to figure out.

Calculator (Arithmatician in the PSP remake) is a rather confusing Job to use, but if used properly is the strongest mage Job in the game. The key to using it by using their parameter abilities - I'm a little rusty on the specifics, but from what I remember, one can either determine level, HP, faith or brave, one is the actual number the ability will effect, and the third one is whatever spell you want to use.

For example, setting it as 'Level 5 Fire 3' will automatically cast (with no MP use or charge time!) Fire 3 on all enemies on the battlefield who have a level which is a multiple of 5 (such as 20, 25 etc). Naturally, this can be devastatingly effective if used correctly. However, if you were like me and flunked maths, then it can be quite hard to use right. The main benefit of Math Magic is that Calculator uses nearly every White, Black, Time and Oracle spell you've previously learned, takes no time to cast (the effect is immediate) and consumes no MP. And yes, this is as overpowered as it sounds! Calculator doesn't work with all Jobs though (for instance, it doesn't work with Geomancer, Chemist or Summoner abilities), only 'basic' magic.

But like I said, Calculator is the supreme mage Job in FFT so it's to be expected I guess. :p

Incidentally, I think it would be better in your case to just stick with using Level as the determining parameter ability as it's easier to, no pun intended, calculate your spells. ;)