81952821757521 has 256 divisors, whose sum is σ = 149186644992000. Its totient is φ = 43779082798080.

The previous prime is 81952821757489. The next prime is 81952821757549. The reversal of 81952821757521 is 12575712825918.

It is a happy number.

81952821757521 is a `hidden beast` number, since 8 + 1 + 9 + 5 + 28 + 2 + 17 + 575 + 21 = 666.

It is not a de Polignac number, because 81952821757521 - 2⁵ = 81952821757489 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81952821757591) 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 255 ways as a sum of consecutive naturals, for example, 6871195660 + ... + 6871207586.

It is an arithmetic number, because the mean of its divisors is an integer number (582760332000).

Almost surely, 2^{81952821757521} is an apocalyptic number.

It is an amenable number.

81952821757521 is a deficient number, since it is larger than the sum of its proper divisors (67233823234479).

81952821757521 is a wasteful number, since it uses less digits than its factorization.

81952821757521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12661 (or 12655 counting only the distinct ones).

The product of its digits is 28224000, while the sum is 63.

The spelling of 81952821757521 in words is "eighty-one trillion, nine hundred fifty-two billion, eight hundred twenty-one million, seven hundred fifty-seven thousand, five hundred twenty-one".