81956861 has 24 divisors (see below), whose sum is σ = 102545280. Its totient is φ = 65100672.

The previous prime is 81956857. The next prime is 81956867. The reversal of 81956861 is 16865918.

It is not a de Polignac number, because 81956861 - 2² = 81956857 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81956867) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 42821 + ... + 44693.

It is an arithmetic number, because the mean of its divisors is an integer number (4272720).

Almost surely, 2^81956861 is an apocalyptic number.

It is an amenable number.

81956861 is a deficient number, since it is larger than the sum of its proper divisors (20588419).

81956861 is a wasteful number, since it uses less digits than its factorization.

81956861 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1953 (or 1946 counting only the distinct ones).

The product of its digits is 103680, while the sum is 44.

The square root of 81956861 is about 9053.0028719757. The cubic root of 81956861 is about 434.3719496085.

The spelling of 81956861 in words is "eighty-one million, nine hundred fifty-six thousand, eight hundred sixty-one".