When to use 'divisible' vs 'dividable'

In common usage there may be little or no difference in meaning; but in mathematical writing, divisible has an accepted usage not held by dividable. Oxford Dictionary gives “Mathematics (of a number) containing another number a number of times without a remainder: 24 is divisible by 4” as sense 2 of divisible. Sometimes redundant wording like evenly divisible is used, and I suppose evenly dividable could be used, but it isn't.

I don't know of a general rule. Incidentally, as seen via links in google books, dividable is a word respectable enough to use, in spite of suffering some disrespect, as in following:

Use dividable only if you want to appear strange... GoogleFight:

Actually both are correct, the difference is the origin of the word. Divisible comes from the Latin root of certain words in English, it is the same word in French; while dividable comes from the Germanic root of English.

The same can be applied to various words in the English language, those that find their roots from Latin are generally employed by higher classes of English society such as scientific terms, while its Germanic counter-part are mostly used in its popular usage.