A radial annular flange of a rotor or stator element of a turbomachine including, at an inner/outer periphery, alternating solid portions and hollow portions, the solid portions including orifices for passing fastener bolts. The flange in the bottom of at least one hollow portion has a radius relative to the axis of the turbomachine that is less/greater than the radius of a circle that is tangential to the outsides/insides of the orifices for passing bolts through the solid portions.