81339793920 has 2560 divisors, whose sum is σ = 407288217600. Its totient is φ = 14863564800.

The previous prime is 81339793919. The next prime is 81339793957. The reversal of 81339793920 is 2939793318.

81339793920 is a `hidden beast` number, since 81 + 3 + 397 + 93 + 92 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (2560).

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 (13) of ones.

It is a polite number, since it can be written in 255 ways as a sum of consecutive naturals, for example, 2623864305 + ... + 2623864335.

It is an arithmetic number, because the mean of its divisors is an integer number (159096960).

Almost surely, 2^81339793920 is an apocalyptic number.

81339793920 is a gapful number since it is divisible by the number (80) 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 81339793920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (203644108800).

81339793920 is an abundant number, since it is smaller than the sum of its proper divisors (325948423680).

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

81339793920 is a wasteful number, since it uses less digits than its factorization.

81339793920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127 (or 105 counting only the distinct ones).

The product of its (nonzero) digits is 2204496, while the sum is 54.

The spelling of 81339793920 in words is "eighty-one billion, three hundred thirty-nine million, seven hundred ninety-three thousand, nine hundred twenty".