81956021 has 8 divisors (see below), whose sum is σ = 94402560. Its totient is φ = 69694128.

The previous prime is 81955927. The next prime is 81956027. The reversal of 81956021 is 12065918.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 81956021 - 2¹⁰ = 81954997 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81956027) 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 7 ways as a sum of consecutive naturals, for example, 45206 + ... + 46983.

It is an arithmetic number, because the mean of its divisors is an integer number (11800320).

Almost surely, 2^81956021 is an apocalyptic number.

It is an amenable number.

81956021 is a deficient number, since it is larger than the sum of its proper divisors (12446539).

81956021 is a wasteful number, since it uses less digits than its factorization.

81956021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 92323.

The product of its (nonzero) digits is 4320, while the sum is 32.

The square root of 81956021 is about 9052.9564784108. The cubic root of 81956021 is about 434.3704656014.

The spelling of 81956021 in words is "eighty-one million, nine hundred fifty-six thousand, twenty-one".