18354551221 has 4 divisors (see below), whose sum is σ = 18802223244. Its totient is φ = 17906879200.

The previous prime is 18354551203. The next prime is 18354551231. The reversal of 18354551221 is 12215545381.

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

It can be written as a sum of positive squares in 2 ways, for example, as 2576679121 + 15777872100 = 50761^2 + 125610^2 .

It is a cyclic number.

It is not a de Polignac number, because 18354551221 - 2²⁵ = 18320996789 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 (18354551231) 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, 223835950 + ... + 223836031.

It is an arithmetic number, because the mean of its divisors is an integer number (4700555811).

Almost surely, 2^18354551221 is an apocalyptic number.

It is an amenable number.

18354551221 is a deficient number, since it is larger than the sum of its proper divisors (447672023).

18354551221 is an equidigital number, since it uses as much as digits as its factorization.

18354551221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 447672022.

The product of its digits is 48000, while the sum is 37.

The spelling of 18354551221 in words is "eighteen billion, three hundred fifty-four million, five hundred fifty-one thousand, two hundred twenty-one".