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 = p q r has precisely eight positive divisors, namely 1, p, q, r, p q, q r, p r, and n itself. The Möbius function of a sphenic number is -1.

almost prime | composite number | divisor | positive integer | prime factorization | prime number | product | semiprime