The classic “missing number 7” phenomenon, though widely publicized as one representative case of hypnosis, remains much of a hype lacking empirical support. Here we examined the conversion between the magnitude and ordinal forms of numerical representation and the corresponding brain activities with FMRI, under the influence of hypnotic suggestion. Two groups of participants performed visual parity judgments by making spatial and non-spatial responses before receiving hypnotic suggestions that either manipulated magnitude or ordinal representations, respectively. We found a significant interaction between the type of suggestion and response under the manipulated magnitude condition, indicating that seeing a number line could elicit the magnitude representation, yet thinking of the magnitude of numbers does not directly elicit the spatial numerical mapping. Furthermore, the linkage between numbers and spatial response correlated with the activation in the right superior frontal area and left angular gyrus under the magnitude suggestion, and in the right dorsolateral prefrontal cortex under the order suggestion. On the other hand, the linkage between numbers and non-spatial response correlated with the activation in the left ventral intraparietal area under the magnitude suggestion, and right intraparietal sulcus, left ventrolateral prefrontal cortex and left posterior intraparietal sulcus under the order suggestion. Taken together, the current findings indicate that the ordinal and magnitude forms of a number may share distinct features and supported by different brain networks. In addition to demonstrate empirical supports for the effect of hypnotic suggestion on the processing of numbers, the current study also indicates a malleable mapping between number and response codes prone to the influence of task demand and individual differences.