Sphenic Number

A sphenic number is a positive integer n which is the product of exactly three distinct primes. The first few sphenic numbers are 30, 42, 66, 70, 78, 102, 105, 110, 114, ... (OEIS A007304).

In particular, if p, q, and r are prime numbers, then every sphenic number n=pqr has precisely eight positive divisors, namely 1, p, q, r, pq, qr, pr, and n itself.

The Möbius function of a sphenic number is -1.

See also

Almost Prime, Composite Number, Divisor, Positive Integer, Prime Factorization, Prime Number, Product, Semiprime

Portions of this entry contributed by Christopher Stover

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Sloane, N. J. A. Sequence A007304/M5207 in "The On-Line Encyclopedia of Integer Sequences."

Cite this as:

Stover, Christopher and Weisstein, Eric W. "Sphenic Number." From MathWorld--A Wolfram Web Resource.

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