81861585 has 16 divisors (see below), whose sum is σ = 141054144. Its totient is φ = 40300992.

The previous prime is 81861581. The next prime is 81861599. The reversal of 81861585 is 58516818.

It is a happy number.

It is not a de Polignac number, because 81861585 - 2² = 81861581 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81861581) 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 15 ways as a sum of consecutive naturals, for example, 209707 + ... + 210096.

It is an arithmetic number, because the mean of its divisors is an integer number (8815884).

Almost surely, 2^81861585 is an apocalyptic number.

It is an amenable number.

81861585 is a deficient number, since it is larger than the sum of its proper divisors (59192559).

81861585 is a wasteful number, since it uses less digits than its factorization.

81861585 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 419824.

The product of its digits is 76800, while the sum is 42.

The square root of 81861585 is about 9047.7392203799. The cubic root of 81861585 is about 434.2035631806.

The spelling of 81861585 in words is "eighty-one million, eight hundred sixty-one thousand, five hundred eighty-five".