18173408521 has 4 divisors (see below), whose sum is σ = 18239016772. Its totient is φ = 18107800272.

The previous prime is 18173408503. The next prime is 18173408567. The reversal of 18173408521 is 12580437181.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12580437181 = 13 ⋅967725937.

It can be written as a sum of positive squares in 2 ways, for example, as 3290628496 + 14882780025 = 57364^2 + 121995^2 .

It is a cyclic number.

It is not a de Polignac number, because 18173408521 - 2¹¹ = 18173406473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (18173408921) 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, 32803710 + ... + 32804263.

It is an arithmetic number, because the mean of its divisors is an integer number (4559754193).

Almost surely, 2^18173408521 is an apocalyptic number.

It is an amenable number.

18173408521 is a deficient number, since it is larger than the sum of its proper divisors (65608251).

18173408521 is an equidigital number, since it uses as much as digits as its factorization.

18173408521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 65608250.

The product of its (nonzero) digits is 53760, while the sum is 40.

The spelling of 18173408521 in words is "eighteen billion, one hundred seventy-three million, four hundred eight thousand, five hundred twenty-one".