<p>Language-specific effects are observed in the performance of numerical tasks. We evaluated the effect of the number word system (non-inverted; decade-unit format HDU vs inverted; unit-decade format HUD) in multi-digit numbers on transcoding performance among Arabic-Hebrew bilingual university students. Both languages are written right-to-left, but only in Arabic the sequence of number words is inverted, with units stipulated before decades (e.g. ‘four-and-twenty’). Previously we (Hayek et al., Writing Systems Research 11:188–202, 2019) addressed the effect of the number word system on transcoding by handwriting while in the present study, participants were asked to type the numerals. We found that the transcoding ability of verbally presented numbers in the standard inverted format, of bilingual adult native speakers of Arabic was inferior to their ability to transcode multi-digit number words in Arabic in a nonstandard format (HDU). These results were replicated in the present study. In addition, we found that native speakers of Arabic were actually most fluent in transcoding when the number words were presented in Hebrew, a language in which they had high proficiency, and were equal in transcoding ability when number words were presented in English, a language in which they were less proficient. The results suggest that even in a highly proficient bilingual adult, transcoding routines may be affected by the number word system regardless of language dominance.</p>