"Orthotopic" or "orthotopal"

An n-orthotope is a fancy name for an n-dimensional cube. I'd like to describe an object that has this quality. Which is the correct adjective: orthotopic or orthotopal?

There is a similar word polytope used in mathematics, and it seems you should use the same adjectival form for polytope and orthotope. Looking at the arXiv, if we use Google to search the arXiv for the word polytopal, we get 715 hits, whereas the word polytopic only gives 119 hits. Looking at a few examples gives me the general sense that in mathematics, polytopal and polytopic are synonyms. So I'd suggest using orthotopal.

Note that Google Ngrams suggests that polytopic is more widely used than polytopal among the general public, but it seems to me that you would be more interested in what a mathematical audience uses. Many of the uses of polytopic appear to be in biochemistry. Also note that isotopic is a word, but isotopal does not seem to be one.