81587520 has 448 divisors, whose sum is σ = 351129600. Its totient is φ = 17418240.

The previous prime is 81587491. The next prime is 81587521. The reversal of 81587520 is 2578518.

81587520 is a `hidden beast` number, since 81 + 58 + 7 + 520 = 666.

It is a tau number, because it is divible by the number of its divisors (448).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81587521) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 1149085 + ... + 1149155.

Almost surely, 2^81587520 is an apocalyptic number.

81587520 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 81587520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (175564800).

81587520 is an abundant number, since it is smaller than the sum of its proper divisors (269542080).

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

81587520 is a wasteful number, since it uses less digits than its factorization.

81587520 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123 (or 107 counting only the distinct ones).

The product of its (nonzero) digits is 22400, while the sum is 36.

The square root of 81587520 is about 9032.5810264841. The cubic root of 81587520 is about 433.7184636579.

The spelling of 81587520 in words is "eighty-one million, five hundred eighty-seven thousand, five hundred twenty".