81965521 has 12 divisors (see below), whose sum is σ = 90799632. Its totient is φ = 73931000.

The previous prime is 81965479. The next prime is 81965557. The reversal of 81965521 is 12556918.

It is not a de Polignac number, because 81965521 - 2⁷ = 81965393 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81965561) 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 11 ways as a sum of consecutive naturals, for example, 13266 + ... + 18436.

It is an arithmetic number, because the mean of its divisors is an integer number (7566636).

Almost surely, 2^81965521 is an apocalyptic number.

It is an amenable number.

81965521 is a deficient number, since it is larger than the sum of its proper divisors (8834111).

81965521 is a wasteful number, since it uses less digits than its factorization.

81965521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5324 (or 5313 counting only the distinct ones).

The product of its digits is 21600, while the sum is 37.

The square root of 81965521 is about 9053.4811536778. The cubic root of 81965521 is about 434.3872484237.

The spelling of 81965521 in words is "eighty-one million, nine hundred sixty-five thousand, five hundred twenty-one".