Educated adults and children engage a network of frontal and parietal brain regions for numerical thinking. Recent studies document some prominent changes as this network emerges over development, including a unilateral right to bilateral shift in number-selective parietal brain activity, a strengthening of intra- and interhemispheric parietal connections, reduced engagement of prefrontal regions, and decoupling between prefrontal and parietal regions. Based on these findings, it appears that right parietal regions form an innate or early-emerging basis for representing numerical magnitudes, whereas left parietal regions support the representation of culturally acquired symbolic numbers that begin to emerge over childhood. Functional connections between parietal hemispheres and the parietal and prefrontal cortex likely support associations between magnitudes and symbols, as they are associated with numerical proficiency. Prefrontal regions appear to provide general cognitive resources to support these associations, engaging and correlating positively during the learning process and disengaging and correlating negatively after mastery.