81666589 has 16 divisors (see below), whose sum is σ = 90402048. Its totient is φ = 73446912.

The previous prime is 81666551. The next prime is 81666593. The reversal of 81666589 is 98566618.

It is a cyclic number.

It is not a de Polignac number, because 81666589 - 2¹³ = 81658397 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81666509) 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, 33169 + ... + 35545.

It is an arithmetic number, because the mean of its divisors is an integer number (5650128).

Almost surely, 2^81666589 is an apocalyptic number.

It is an amenable number.

81666589 is a deficient number, since it is larger than the sum of its proper divisors (8735459).

81666589 is a wasteful number, since it uses less digits than its factorization.

81666589 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2484.

The product of its digits is 622080, while the sum is 49.

The square root of 81666589 is about 9036.9568439824. The cubic root of 81666589 is about 433.8585284326.

The spelling of 81666589 in words is "eighty-one million, six hundred sixty-six thousand, five hundred eighty-nine".