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Published online by Cambridge University Press: 26 February 2010
For each natural number m, let N(m) denote the number of integers n with ø(n) = m, where ø denotes Euler's function. There are many interesting problems connected with the function N(m), such as the conjecture of Carmichael that N(m) is never 1 (see [9], for example) and the study of the distribution of the m for which N(m) > 0 (see Erdős and Hall [5]). In this note we shall be concerned with the maximal order of N(m).