81553920 has 320 divisors, whose sum is σ = 313479936. Its totient is φ = 17694720.

The previous prime is 81553907. The next prime is 81553931. The reversal of 81553920 is 2935518.

It is a tau number, because it is divible by the number of its divisors (320).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1989100 + ... + 1989140.

Almost surely, 2^81553920 is an apocalyptic number.

81553920 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 81553920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (156739968).

81553920 is an abundant number, since it is smaller than the sum of its proper divisors (231926016).

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

81553920 is a wasteful number, since it uses less digits than its factorization.

81553920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111 (or 95 counting only the distinct ones).

The product of its (nonzero) digits is 10800, while the sum is 33.

The square root of 81553920 is about 9030.7209014563. The cubic root of 81553920 is about 433.6589163916.

The spelling of 81553920 in words is "eighty-one million, five hundred fifty-three thousand, nine hundred twenty".