18421618 has 4 divisors (see below), whose sum is σ = 27632430. Its totient is φ = 9210808.

The previous prime is 18421609. The next prime is 18421619. The reversal of 18421618 is 81612481.

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

It can be written as a sum of positive squares in only one way, i.e., 10452289 + 7969329 = 3233^2 + 2823^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a self number, because there is not a number n which added to its sum of digits gives 18421618.

It is not an unprimeable number, because it can be changed into a prime (18421619) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4605403 + ... + 4605406.

Almost surely, 2^18421618 is an apocalyptic number.

18421618 is a deficient number, since it is larger than the sum of its proper divisors (9210812).

18421618 is an equidigital number, since it uses as much as digits as its factorization.

18421618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9210811.

The product of its digits is 3072, while the sum is 31.

The square root of 18421618 is about 4292.0412393173. The cubic root of 18421618 is about 264.1045748088.

The spelling of 18421618 in words is "eighteen million, four hundred twenty-one thousand, six hundred eighteen".