Catalysis of the reaction: 1-diphospho-1D-myo-inositol 2,3,4,5,6-pentakisphosphate + H2O = 1D-myo-inositol 1,2,3,4,5,6-hexakisphosphate + phosphate + 2 H+.
inositol 1-diphosphate 2,3,4,5,6-pentakisphosphate 1-diphosphatase activity