18154521278209 has 4 divisors (see below), whose sum is σ = 18219128115780. Its totient is φ = 18089914440640.

The previous prime is 18154521278203. The next prime is 18154521278221. The reversal of 18154521278209 is 90287212545181.

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 8921601479025 + 9232919799184 = 2986905^2 + 3038572^2 .

It is a cyclic number.

It is not a de Polignac number, because 18154521278209 - 2¹⁷ = 18154521147137 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 18154521278209.

It is not an unprimeable number, because it can be changed into a prime (18154521278203) 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, 32303418364 + ... + 32303418925.

It is an arithmetic number, because the mean of its divisors is an integer number (4554782028945).

Almost surely, 2^{18154521278209} is an apocalyptic number.

It is an amenable number.

18154521278209 is a deficient number, since it is larger than the sum of its proper divisors (64606837571).

18154521278209 is an equidigital number, since it uses as much as digits as its factorization.

18154521278209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64606837570.

The product of its (nonzero) digits is 3225600, while the sum is 55.

The spelling of 18154521278209 in words is "eighteen trillion, one hundred fifty-four billion, five hundred twenty-one million, two hundred seventy-eight thousand, two hundred nine".