81587205 has 72 divisors (see below), whose sum is σ = 166244832. Its totient is φ = 36904896.

The previous prime is 81587201. The next prime is 81587221. The reversal of 81587205 is 50278518.

It is not a de Polignac number, because 81587205 - 2² = 81587201 is a prime.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 81587205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81587201) 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 71 ways as a sum of consecutive naturals, for example, 359302 + ... + 359528.

It is an arithmetic number, because the mean of its divisors is an integer number (2308956).

Almost surely, 2^81587205 is an apocalyptic number.

It is an amenable number.

81587205 is an abundant number, since it is smaller than the sum of its proper divisors (84657627).

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

81587205 is a wasteful number, since it uses less digits than its factorization.

81587205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 415 (or 405 counting only the distinct ones).

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

The square root of 81587205 is about 9032.5635895907. The cubic root of 81587205 is about 433.7179054782.

The spelling of 81587205 in words is "eighty-one million, five hundred eighty-seven thousand, two hundred five".