16518921 has 4 divisors (see below), whose sum is σ = 22025232. Its totient is φ = 11012612.

The previous prime is 16518919. The next prime is 16518959. The reversal of 16518921 is 12981561.

16518921 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 16518921 - 2¹ = 16518919 is a prime.

It is not an unprimeable number, because it can be changed into a prime (16518721) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2753151 + ... + 2753156.

It is an arithmetic number, because the mean of its divisors is an integer number (5506308).

Almost surely, 2^16518921 is an apocalyptic number.

It is an amenable number.

16518921 is a deficient number, since it is larger than the sum of its proper divisors (5506311).

16518921 is an equidigital number, since it uses as much as digits as its factorization.

16518921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5506310.

The product of its digits is 4320, while the sum is 33.

The square root of 16518921 is about 4064.3475491154. The cubic root of 16518921 is about 254.6794434151.

The spelling of 16518921 in words is "sixteen million, five hundred eighteen thousand, nine hundred twenty-one".