18561438720 has 396 divisors, whose sum is σ = 70714474740. Its totient is φ = 4498391040.

The previous prime is 18561438671. The next prime is 18561438743. The reversal of 18561438720 is 2783416581.

18561438720 is a `hidden beast` number, since 1 + 8 + 5 + 614 + 3 + 8 + 7 + 20 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 6959563776 + 11601874944 = 83424^2 + 107712^2 .

It is a tau number, because it is divible by the number of its divisors (396).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 5574016 + ... + 5577344.

Almost surely, 2^18561438720 is an apocalyptic number.

18561438720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18561438720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35357237370).

18561438720 is an abundant number, since it is smaller than the sum of its proper divisors (52153036020).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18561438720 is a wasteful number, since it uses less digits than its factorization.

18561438720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3382 (or 3350 counting only the distinct ones).

The product of its (nonzero) digits is 322560, while the sum is 45.

The spelling of 18561438720 in words is "eighteen billion, five hundred sixty-one million, four hundred thirty-eight thousand, seven hundred twenty".