18331729920 has 640 divisors, whose sum is σ = 76504032000. Its totient is φ = 4076863488.

The previous prime is 18331729907. The next prime is 18331729939. The reversal of 18331729920 is 2992713381.

18331729920 is a `hidden beast` number, since 1 + 8 + 331 + 7 + 299 + 20 = 666.

It is a tau number, because it is divible by the number of its divisors (640).

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

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 495452142 + ... + 495452178.

It is an arithmetic number, because the mean of its divisors is an integer number (119537550).

Almost surely, 2^18331729920 is an apocalyptic number.

18331729920 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 18331729920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (38252016000).

18331729920 is an abundant number, since it is smaller than the sum of its proper divisors (58172302080).

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

18331729920 is an frugal number, since it uses more digits than its factorization.

18331729920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96 (or 54 counting only the distinct ones).

The product of its (nonzero) digits is 163296, while the sum is 45.

The spelling of 18331729920 in words is "eighteen billion, three hundred thirty-one million, seven hundred twenty-nine thousand, nine hundred twenty".