Atypical, so far as I know, means irregular, unusual or not typical/normal. Here in India, people generally use 'typical' to mean difficult or hard. (A question about that was also asked here some four years back by an Indian.) I understand now that typical cannot be used in that sense. But on that note, can 'atypical' be used to mean difficult or hard? For example,
The teacher dictated the whole passage orally, but wrote some atypical words on blackboard.
Her new song is quite atypical. (in the sense of being difficult to sing)