Composite Numbers Day - December 14

Happy Composite Numbers Day!

Composite numbers are sort of like the complement of the prime numbers (ignoring 1, which is neither), and each of them can be expressed as two or more prime numbers. For example, 12 = 2 X 2 X 3 (2 and 3 are primes) so it is composite, and 35 = 5 X 7 (5 and 7 are primes) so it is composite. Every positive integer greater than 1 is going to be either a prime number or a composite number.

A subset of the composite numbers, the semiprime numbers, are the driving force behind public key cryptography Other interesting subsets of the composite numbers are the sphenic numbers and the powerful numbers.

December 14 was chosen for Composite Numbers Day since they are the largest consecutive composite numbers to form a date: 12/14.



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