18561433644 has 288 divisors, whose sum is σ = 54493770240. Its totient is φ = 5283532800.

The previous prime is 18561433643. The next prime is 18561433651. The reversal of 18561433644 is 44633416581.

18561433644 is a `hidden beast` number, since 1 + 8 + 561 + 43 + 3 + 6 + 44 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 18561433644.

It is not an unprimeable number, because it can be changed into a prime (18561433643) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 66054784 + ... + 66055064.

It is an arithmetic number, because the mean of its divisors is an integer number (189214480).

Almost surely, 2^18561433644 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 18561433644, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27246885120).

18561433644 is an abundant number, since it is smaller than the sum of its proper divisors (35932336596).

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

18561433644 is a wasteful number, since it uses less digits than its factorization.

18561433644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 521 (or 516 counting only the distinct ones).

The product of its digits is 829440, while the sum is 45.

The spelling of 18561433644 in words is "eighteen billion, five hundred sixty-one million, four hundred thirty-three thousand, six hundred forty-four".