81335520 has 144 divisors (see below), whose sum is σ = 317247840. Its totient is φ = 18588672.

The previous prime is 81335483. The next prime is 81335539. The reversal of 81335520 is 2553318.

81335520 is a `hidden beast` number, since 8 + 133 + 5 + 520 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

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, 6046 + ... + 14114.

It is an arithmetic number, because the mean of its divisors is an integer number (2203110).

Almost surely, 2^81335520 is an apocalyptic number.

81335520 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 81335520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (158623920).

81335520 is an abundant number, since it is smaller than the sum of its proper divisors (235912320).

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

81335520 is a wasteful number, since it uses less digits than its factorization.

81335520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8097 (or 8086 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

The square root of 81335520 is about 9018.6207371194. The cubic root of 81335520 is about 433.2714599364.

Adding to 81335520 its reverse (2553318), we get a palindrome (83888838).

The spelling of 81335520 in words is "eighty-one million, three hundred thirty-five thousand, five hundred twenty".