18211121 has 4 divisors (see below), whose sum is σ = 18388032. Its totient is φ = 18034212.

The previous prime is 18211111. The next prime is 18211129. The reversal of 18211121 is 12111281.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 18211121 - 2⁶ = 18211057 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 18211121.

It is not an unprimeable number, because it can be changed into a prime (18211129) 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 3 ways as a sum of consecutive naturals, for example, 88301 + ... + 88506.

It is an arithmetic number, because the mean of its divisors is an integer number (4597008).

Almost surely, 2^18211121 is an apocalyptic number.

It is an amenable number.

18211121 is a deficient number, since it is larger than the sum of its proper divisors (176911).

18211121 is a wasteful number, since it uses less digits than its factorization.

18211121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 176910.

The product of its digits is 32, while the sum is 17.

The square root of 18211121 is about 4267.4490037961. The cubic root of 18211121 is about 263.0947771005.

The spelling of 18211121 in words is "eighteen million, two hundred eleven thousand, one hundred twenty-one".