81521175729 has 32 divisors (see below), whose sum is σ = 125427087360. Its totient is φ = 46132204032.

The previous prime is 81521175679. The next prime is 81521175739. The reversal of 81521175729 is 92757112518.

It is not a de Polignac number, because 81521175729 - 2¹⁵ = 81521142961 is a prime.

It is not an unprimeable number, because it can be changed into a prime (81521175739) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 10136692 + ... + 10144730.

It is an arithmetic number, because the mean of its divisors is an integer number (3919596480).

Almost surely, 2^81521175729 is an apocalyptic number.

It is an amenable number.

81521175729 is a deficient number, since it is larger than the sum of its proper divisors (43905911631).

81521175729 is a wasteful number, since it uses less digits than its factorization.

81521175729 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12669.

The product of its digits is 352800, while the sum is 48.

The spelling of 81521175729 in words is "eighty-one billion, five hundred twenty-one million, one hundred seventy-five thousand, seven hundred twenty-nine".