81868320 has 120 divisors (see below), whose sum is σ = 288972684. Its totient is φ = 21828096.

The previous prime is 81868301. The next prime is 81868327. The reversal of 81868320 is 2386818.

It can be written as a sum of positive squares in 2 ways, for example, as 81649296 + 219024 = 9036^2 + 468^2 .

It is a tau number, because it is divible by the number of its divisors (120).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (81868327) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 9802 + ... + 16118.

Almost surely, 2^81868320 is an apocalyptic number.

81868320 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 81868320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (144486342).

81868320 is an abundant number, since it is smaller than the sum of its proper divisors (207104364).

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

81868320 is a wasteful number, since it uses less digits than its factorization.

81868320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6344 (or 6327 counting only the distinct ones).

The product of its (nonzero) digits is 18432, while the sum is 36.

The square root of 81868320 is about 9048.1114051497. Note that the first 3 decimals coincide. The cubic root of 81868320 is about 434.2154706005.

The spelling of 81868320 in words is "eighty-one million, eight hundred sixty-eight thousand, three hundred twenty".