Plasma membrane Na(+)/H(+) antiporter. Mediates the electroneutral exchange of intracellular H(+) ions for extracellular Na(+) (PubMed:10444453). Major apical Na(+)/H(+) exchanger in the base of the colonic crypt. Controls in the colonic crypt intracellular pH (pHi) to direct colonic epithelial cell differentiation into the absorptive enterocyte lineage at the expense of the secretory lineage (By similarity). {ECO:0000250|UniProtKB:Q3ZAS0, ECO:0000269|PubMed:10444453}. This is the function of ENSG00000115616 (SLC9A2, solute carrier family 9 member A2).