81666585 has 192 divisors, whose sum is σ = 199180800. Its totient is φ = 30481920.

The previous prime is 81666551. The next prime is 81666593. The reversal of 81666585 is 58566618.

81666585 = T₄₁₉ + T₄₂₀ + ... + T₈₂₅.

It is not a de Polignac number, because 81666585 - 2¹⁵ = 81633817 is a prime.

It is a super-2 number, since 2×81666585² = 13338862211124450, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a self number, because there is not a number n which added to its sum of digits gives 81666585.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 2207187 + ... + 2207223.

It is an arithmetic number, because the mean of its divisors is an integer number (1037400).

Almost surely, 2^81666585 is an apocalyptic number.

It is an amenable number.

81666585 is an abundant number, since it is smaller than the sum of its proper divisors (117514215).

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

81666585 is a wasteful number, since it uses less digits than its factorization.

81666585 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 93 (or 76 counting only the distinct ones).

The product of its digits is 345600, while the sum is 45.

The square root of 81666585 is about 9036.9566226689. The cubic root of 81666585 is about 433.8585213492.

It can be divided in two parts, 81 and 666585, that added together give a palindrome (666666).

The spelling of 81666585 in words is "eighty-one million, six hundred sixty-six thousand, five hundred eighty-five".