81601920 has 192 divisors, whose sum is σ = 291507840. Its totient is φ = 21012480.

The previous prime is 81601901. The next prime is 81601937. The reversal of 81601920 is 2910618.

It is a tau number, because it is divible by the number of its divisors (192).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 178332 + ... + 178788.

It is an arithmetic number, because the mean of its divisors is an integer number (1518270).

Almost surely, 2^81601920 is an apocalyptic number.

81601920 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 81601920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (145753920).

81601920 is an abundant number, since it is smaller than the sum of its proper divisors (209905920).

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

81601920 is a wasteful number, since it uses less digits than its factorization.

81601920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 513 (or 498 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 81601920 is about 9033.3781056701. The cubic root of 81601920 is about 433.7439789102.

The spelling of 81601920 in words is "eighty-one million, six hundred one thousand, nine hundred twenty".