18109921 has 8 divisors (see below), whose sum is σ = 18746624. Its totient is φ = 17476560.

The previous prime is 18109849. The next prime is 18109937. The reversal of 18109921 is 12990181.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a de Polignac number, because none of the positive numbers 2^k-18109921 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (31).

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18109951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 15655 + ... + 16771.

It is an arithmetic number, because the mean of its divisors is an integer number (2343328).

Almost surely, 2^18109921 is an apocalyptic number.

It is an amenable number.

18109921 is a deficient number, since it is larger than the sum of its proper divisors (636703).

18109921 is a wasteful number, since it uses less digits than its factorization.

18109921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1671.

The product of its (nonzero) digits is 1296, while the sum is 31.

The square root of 18109921 is about 4255.5752842595. The cubic root of 18109921 is about 262.6065284934.

The spelling of 18109921 in words is "eighteen million, one hundred nine thousand, nine hundred twenty-one".