Abstract Here we review the contribution of brain stimulation studies to the understanding of number and arithmetic processes. We show that these studies have significantly contributed to detail the architecture of numerical processing and its critical relation with brain regions such as the parietal and the frontal areas. We also present studies that aimed to boost number and arithmetic learning combining brain stimulation and training in healthy adults. These indicate that stimulation of suitable brain areas may induce long-term changes when coupled with an appropriate training regime. We claim that despite this progress, some of the findings thus far are still relatively heterogeneous, and that studies focusing on atypical and developing populations, such as people with dyscalculia, are currently scarce. Ultimately therefore, this promising progress indicates the need of future detailed and well-controlled investigations to fully benefit from the use of brain stimulation, also combined with training.