In the astrological work Tājikamuktāvali by Tuka (1.41) there is a compound khābdhīrakebhyaḥ which, from the context, has to mean 'from forty and ten, [respectively]'. This is supported by the explicatory numerals inserted by several mss: khābdhī 40 rakebhyaḥ 10, etc; but I haven't found anything like iraka/īraka in any dictionary or list of bhūtasaṃkhyā numerals. (Some mss emend to -īkhakebhyaḥ, which doesn't really help.) If anyone has come across this way of expressing the value 10 elsewhere, I'd be grateful for a reference, and even more so for an explanation of the word.