18121618 has 4 divisors (see below), whose sum is σ = 27182430. Its totient is φ = 9060808.

The previous prime is 18121613. The next prime is 18121633. The reversal of 18121618 is 81612181.

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., 12299049 + 5822569 = 3507^2 + 2413^2 .

It is an alternating number because its digits alternate between odd and even.

It is not an unprimeable number, because it can be changed into a prime (18121613) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4530403 + ... + 4530406.

Almost surely, 2^18121618 is an apocalyptic number.

18121618 is a deficient number, since it is larger than the sum of its proper divisors (9060812).

18121618 is an equidigital number, since it uses as much as digits as its factorization.

18121618 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9060811.

The product of its digits is 768, while the sum is 28.

The square root of 18121618 is about 4256.9493771949. The cubic root of 18121618 is about 262.6630545539.

Adding to 18121618 its reverse (81612181), we get a palindrome (99733799).

The spelling of 18121618 in words is "eighteen million, one hundred twenty-one thousand, six hundred eighteen".