81636585 has 16 divisors (see below), whose sum is σ = 132088320. Its totient is φ = 43049600.

The previous prime is 81636563. The next prime is 81636587. The reversal of 81636585 is 58563618.

It is not a de Polignac number, because 81636585 - 2¹⁸ = 81374441 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is not an unprimeable number, because it can be changed into a prime (81636587) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 29241 + ... + 31910.

It is an arithmetic number, because the mean of its divisors is an integer number (8255520).

Almost surely, 2^81636585 is an apocalyptic number.

It is an amenable number.

81636585 is a deficient number, since it is larger than the sum of its proper divisors (50451735).

81636585 is a wasteful number, since it uses less digits than its factorization.

81636585 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61248.

The product of its digits is 172800, while the sum is 42.

The square root of 81636585 is about 9035.2966193701. The cubic root of 81636585 is about 433.8053892563.

It can be divided in two parts, 816 and 36585, that added together give a triangular number (37401 = T₂₇₃).

The spelling of 81636585 in words is "eighty-one million, six hundred thirty-six thousand, five hundred eighty-five".