81921009014928 has 120 divisors (see below), whose sum is σ = 239288139188280. Its totient is φ = 26138318469120.

The previous prime is 81921009014861. The next prime is 81921009014947. The reversal of 81921009014928 is 82941090012918.

It can be written as a sum of positive squares in 4 ways, for example, as 1731992866704 + 80189016148224 = 1316052^2 + 8954832^2 .

It is a super-2 number, since 2×81921009014928² (a number of 29 digits) contains 22 as substring.

It is an unprimeable number.

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, 130588123 + ... + 131213946.

It is an arithmetic number, because the mean of its divisors is an integer number (1994067826569).

Almost surely, 2^{81921009014928} is an apocalyptic number.

It is an amenable number.

81921009014928 is an abundant number, since it is smaller than the sum of its proper divisors (157367130173352).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81921009014928 is a wasteful number, since it uses less digits than its factorization.

81921009014928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 261802177 (or 261802168 counting only the distinct ones).

The product of its (nonzero) digits is 746496, while the sum is 54.

The spelling of 81921009014928 in words is "eighty-one trillion, nine hundred twenty-one billion, nine million, fourteen thousand, nine hundred twenty-eight".