81859561 has 16 divisors (see below), whose sum is σ = 97592320. Its totient is φ = 67184640.

The previous prime is 81859549. The next prime is 81859579. The reversal of 81859561 is 16595818.

It is a 8-Lehmer number, since φ(81859561) divides (81859561-1)⁸.

It is a cyclic number.

It is not a de Polignac number, because 81859561 - 2⁵ = 81859529 is a prime.

It is a super-2 number, since 2×81859561² = 13401975454225442, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81859511) 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, 19105 + ... + 22993.

It is an arithmetic number, because the mean of its divisors is an integer number (6099520).

Almost surely, 2^81859561 is an apocalyptic number.

It is an amenable number.

81859561 is a deficient number, since it is larger than the sum of its proper divisors (15732759).

81859561 is a wasteful number, since it uses less digits than its factorization.

81859561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4024.

The product of its digits is 86400, while the sum is 43.

The square root of 81859561 is about 9047.6273685425. The cubic root of 81859561 is about 434.1999846390.

The spelling of 81859561 in words is "eighty-one million, eight hundred fifty-nine thousand, five hundred sixty-one".