90

This number is a composite.

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There are only 8 positive integers n for which the number of primesn (pi(n)) equals the number of positive integers ≤ n relative prime to n (phi(n)). They are 2, 3, 4, 8, 10, 14, 20, and 90. [Moser]

Submitted: 2000-11-02 15:09:13;   Last Modified: 2009-09-16 16:19:40.
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