18661531328 has 56 divisors (see below), whose sum is σ = 40525897104. Its totient is φ = 8455654400.

The previous prime is 18661531313. The next prime is 18661531333. The reversal of 18661531328 is 82313516681.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 181358 + ... + 264978.

It is an arithmetic number, because the mean of its divisors is an integer number (723676734).

Almost surely, 2^18661531328 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 18661531328, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (20262948552).

18661531328 is an abundant number, since it is smaller than the sum of its proper divisors (21864365776).

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

18661531328 is a wasteful number, since it uses less digits than its factorization.

18661531328 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 83961 (or 83951 counting only the distinct ones).

The product of its digits is 207360, while the sum is 44.

The spelling of 18661531328 in words is "eighteen billion, six hundred sixty-one million, five hundred thirty-one thousand, three hundred twenty-eight".