81920320 has 56 divisors (see below), whose sum is σ = 198424800. Its totient is φ = 32205312.

The previous prime is 81920309. The next prime is 81920327. The reversal of 81920320 is 2302918.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81920327) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 16711 + ... + 21049.

It is an arithmetic number, because the mean of its divisors is an integer number (3543300).

Almost surely, 2^81920320 is an apocalyptic number.

81920320 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 81920320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (99212400).

81920320 is an abundant number, since it is smaller than the sum of its proper divisors (116504480).

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

81920320 is a wasteful number, since it uses less digits than its factorization.

81920320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4415 (or 4405 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 25.

The square root of 81920320 is about 9050.9844768401. The cubic root of 81920320 is about 434.3073841581.

It can be divided in two parts, 81920 and 320, that multiplied together give a square (26214400 = 5120²).

The spelling of 81920320 in words is "eighty-one million, nine hundred twenty thousand, three hundred twenty".