18912221 has 4 divisors (see below), whose sum is σ = 18973344. Its totient is φ = 18851100.

The previous prime is 18912181. The next prime is 18912241. The reversal of 18912221 is 12221981.

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 18912221 - 2¹⁰ = 18911197 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 (18912241) 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, 30095 + ... + 30716.

It is an arithmetic number, because the mean of its divisors is an integer number (4743336).

Almost surely, 2^18912221 is an apocalyptic number.

It is an amenable number.

18912221 is a deficient number, since it is larger than the sum of its proper divisors (61123).

18912221 is an equidigital number, since it uses as much as digits as its factorization.

18912221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61122.

The product of its digits is 576, while the sum is 26.

The square root of 18912221 is about 4348.8183452520. The cubic root of 18912221 is about 266.4286012467.

The spelling of 18912221 in words is "eighteen million, nine hundred twelve thousand, two hundred twenty-one".