81880920 has 384 divisors, whose sum is σ = 323481600. Its totient is φ = 17740800.

The previous prime is 81880913. The next prime is 81880921. The reversal of 81880920 is 2908818.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81880921) by changing a digit.

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 95 ways as a sum of consecutive naturals, for example, 2641305 + ... + 2641335.

It is an arithmetic number, because the mean of its divisors is an integer number (842400).

Almost surely, 2^81880920 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81880920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (161740800).

81880920 is an abundant number, since it is smaller than the sum of its proper divisors (241600680).

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

81880920 is a wasteful number, since it uses less digits than its factorization.

81880920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111 (or 104 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 36.

The square root of 81880920 is about 9048.8076562606. The cubic root of 81880920 is about 434.2377455345.

The spelling of 81880920 in words is "eighty-one million, eight hundred eighty thousand, nine hundred twenty".