18436921 has 4 divisors (see below), whose sum is σ = 18886644. Its totient is φ = 17987200.

The previous prime is 18436919. The next prime is 18436931. The reversal of 18436921 is 12963481.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12963481 = 2129 ⋅6089.

It can be written as a sum of positive squares in 2 ways, for example, as 4080400 + 14356521 = 2020^2 + 3789^2 .

It is a cyclic number.

It is not a de Polignac number, because 18436921 - 2¹ = 18436919 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18436931) 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, 224800 + ... + 224881.

It is an arithmetic number, because the mean of its divisors is an integer number (4721661).

Almost surely, 2^18436921 is an apocalyptic number.

It is an amenable number.

18436921 is a deficient number, since it is larger than the sum of its proper divisors (449723).

18436921 is an equidigital number, since it uses as much as digits as its factorization.

18436921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 449722.

The product of its digits is 10368, while the sum is 34.

The square root of 18436921 is about 4293.8235874335. The cubic root of 18436921 is about 264.1776858985.

The spelling of 18436921 in words is "eighteen million, four hundred thirty-six thousand, nine hundred twenty-one".