Developing earlier studies of numbers in Mundurucu, this paper argues that the Mundurucu numeral system is far more complex than usually assumed. The mundurucu numeral system provides indirect but insightful arguments for a modular treatment to numbers and numerals. It is argued that distinct components must be distinguished, such as a system of representation of numbers in the format of internal magnitudes, a system of representation for individuals and sets, and one-to-one correspondences between the numerosity expressed by the number and its metrics. It is shown that while many-number systems involve a compositionality of units, sets and sets composed of units, few number languages, such as Mundurucu, do not have acess to sets composed of units in the usual way. The nonconfigurational characater of mundurucu Language, which is related to a property for which we coin the term 'low compositionality power'; accounts for this and accounts for the fact that Mundurucus make use of marked one-to-one strategies in order to overcome the limitations of the core system.