15 (number) - Wikipedia
https://en.wikipedia.org/wiki/15_(number)
15 is: The eighth composite number and the sixth semiprime and the first odd and fourth discrete semiprime; its proper divisors are 1, 3, and 5, so the first of the form (3.q), where q is a higher prime.a deficient number, a lucky number, a bell number (i.e., the number of partitions for a set of size 4), a pentatope number, and a repdigit in binary (1111… See more
DA: 64 PA: 81 MOZ Rank: 27 Up or Down: Up