81983520 has 216 divisors, whose sum is σ = 298702404. Its totient is φ = 20471808.

The previous prime is 81983513. The next prime is 81983521. The reversal of 81983520 is 2538918.

It can be written as a sum of positive squares in 6 ways, for example, as 77369616 + 4613904 = 8796^2 + 2148^2 .

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 (81983521) by changing a digit.

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 35 ways as a sum of consecutive naturals, for example, 416062 + ... + 416258.

Almost surely, 2^81983520 is an apocalyptic number.

81983520 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 81983520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (149351202).

81983520 is an abundant number, since it is smaller than the sum of its proper divisors (216718884).

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

81983520 is a wasteful number, since it uses less digits than its factorization.

81983520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 252 (or 224 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 81983520 is about 9054.4751366382. The cubic root of 81983520 is about 434.4190421330.

The spelling of 81983520 in words is "eighty-one million, nine hundred eighty-three thousand, five hundred twenty".