Composite number
A composite number is a natural number larger than 1 that is not a prime number. The first ten composite numbers are:
- 4, 6, 8, 9, 10, 12, 14, 15, 16 and 18.
Sphenic number
A composite number which has precisely three distinct prime factors is called a sphenic number.
The ten first sphenic numbers are:
- 30; which is also 11-agonal by polygonality and bracketed by twin primes
- 42; which is also a Catalan number
- 66; which is also triangular, hexagonal, 23-agonal and a palindrome
- 70; which is also pentagonal and 13-agonal
- 78
- 102; which is bracketed by twin primes
- 105; which is also 12-agonal
- 110
- 114
- 130; which is also 23-agonal
See also: Highly composite number.