18443921 has 4 divisors (see below), whose sum is σ = 18479844. Its totient is φ = 18408000.

The previous prime is 18443879. The next prime is 18443923. The reversal of 18443921 is 12934481.

It is a happy number.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 4456321 + 13987600 = 2111^2 + 3740^2 .

It is a cyclic number.

It is not a de Polignac number, because 18443921 - 2⁶ = 18443857 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (18443923) 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, 17180 + ... + 18221.

It is an arithmetic number, because the mean of its divisors is an integer number (4619961).

Almost surely, 2^18443921 is an apocalyptic number.

It is an amenable number.

18443921 is a deficient number, since it is larger than the sum of its proper divisors (35923).

18443921 is an equidigital number, since it uses as much as digits as its factorization.

18443921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35922.

The product of its digits is 6912, while the sum is 32.

The square root of 18443921 is about 4294.6386343906. The cubic root of 18443921 is about 264.2111153743.

The spelling of 18443921 in words is "eighteen million, four hundred forty-three thousand, nine hundred twenty-one".