Simultaneous interpreting (SI) is considered to be a highly demanding cognitive task, especially in regard to elements which represent a stumbling block during SI (e.g. numbers, idiomatic expressions, etc.). The current study examines the use of numbers in SI in combination with co-speech gestures. The issue of interpreting numbers has been addressed by different scholars, however it has rarely been studied from the multimodal perspective so far. Given the known role of gesture during processes of lexical retrieval, we hypothesize that the use of co-speech manual gestures plays a significant role in the process of interpreting numbers, i.e. facilitates mental retrieval of the target number. In addition to the hypothesis to be tested, we consider the exploratory question as to whether any gestures with numbers correlate more with an externalized or internalized function, that is: either representation of the numerical concept externally (metaphorical depiction of the quantified entity as an object or space that could be touched or pointed to) or more with self-adapters to help the interpreter manage the cognitive load/stress internally. A corpus of 10 recordings of English-to-Russian SI sessions was analyzed. The interpreting of numbers was analyzed as being correct, incorrect or absent. The analysis of the material showed that the participants mostly interpreted numbers correctly or omitted them in their speech. The results of the analysis of co-speech gestures demonstrated nearly equal use of gesture and no gesture when interpreting numbers, however, there was a significant correlation between interpreting certain number categories and gesture use. Then the following types of gesture functions were analyzed: adapters, pragmatic, representational and deictic. The results indicate that self-adapters were the most frequent gesture type used. This finding can be interpreted based on the literature showing self-adapters ease tension and anxiety and/or help one gain control of stressful situations.