RESUMEN

Some new theorems have been propounded for the numbers (M - 1), as they relate to other numerals, through the basic arithmetical operations, at different bases M. For some reason, we give the proof of the theorems for the case M = 10 using mathematical induction, and by Peano’s fifth axiom make our generalizations. Comments are made in respect of the numbers (M - 1), (in this case 9). Apart from our theorem facilitating mathematical operations, evidences have also been given, from different sources of the interesting properties of this class of numbers, represented in our own case by the numeral 9. The theorems neither violate the divisibility rule for 9 nor are they a consequence of it. From smmetry, a suggestion is made in respect of the possible origin of the numeration in base 10, and the case of a ten dimensional Universe reconsidered.