18122821 has 4 divisors (see below), whose sum is σ = 18378144. Its totient is φ = 17867500.

The previous prime is 18122813. The next prime is 18122843. The reversal of 18122821 is 12822181.

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 18122821 - 2³ = 18122813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18122851) 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, 127555 + ... + 127696.

It is an arithmetic number, because the mean of its divisors is an integer number (4594536).

Almost surely, 2^18122821 is an apocalyptic number.

It is an amenable number.

18122821 is a deficient number, since it is larger than the sum of its proper divisors (255323).

18122821 is an equidigital number, since it uses as much as digits as its factorization.

18122821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 255322.

The product of its digits is 512, while the sum is 25.

The square root of 18122821 is about 4257.0906732180. The cubic root of 18122821 is about 262.6688667035.

The spelling of 18122821 in words is "eighteen million, one hundred twenty-two thousand, eight hundred twenty-one".