81235920 has 80 divisors (see below), whose sum is σ = 256144320. Its totient is φ = 21292032.

The previous prime is 81235919. The next prime is 81235939. The reversal of 81235920 is 2953218.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11292 + ... + 17028.

It is an arithmetic number, because the mean of its divisors is an integer number (3201804).

Almost surely, 2^81235920 is an apocalyptic number.

81235920 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 81235920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (128072160).

81235920 is an abundant number, since it is smaller than the sum of its proper divisors (174908400).

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

81235920 is a wasteful number, since it uses less digits than its factorization.

81235920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5812 (or 5806 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 30.

The square root of 81235920 is about 9013.0971369447. The cubic root of 81235920 is about 433.0945324629.

The spelling of 81235920 in words is "eighty-one million, two hundred thirty-five thousand, nine hundred twenty".