18191998440 has 512 divisors, whose sum is σ = 75968409600. Its totient is φ = 3761925120.

The previous prime is 18191998423. The next prime is 18191998483. The reversal of 18191998440 is 4489919181.

18191998440 is a `hidden beast` number, since 1 + 8 + 1 + 9 + 199 + 8 + 440 = 666.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 23533894 + ... + 23534666.

It is an arithmetic number, because the mean of its divisors is an integer number (148375800).

Almost surely, 2^18191998440 is an apocalyptic number.

18191998440 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 18191998440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (37984204800).

18191998440 is an abundant number, since it is smaller than the sum of its proper divisors (57776411160).

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

18191998440 is a wasteful number, since it uses less digits than its factorization.

18191998440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1094 (or 1084 counting only the distinct ones).

The product of its (nonzero) digits is 746496, while the sum is 54.

The spelling of 18191998440 in words is "eighteen billion, one hundred ninety-one million, nine hundred ninety-eight thousand, four hundred forty".