81985121529 has 16 divisors (see below), whose sum is σ = 111224836800. Its totient is φ = 53702053376.

The previous prime is 81985121521. The next prime is 81985121563. The reversal of 81985121529 is 92512158918.

It is a cyclic number.

It is not a de Polignac number, because 81985121529 - 2³ = 81985121521 is a prime.

It is a Smith number, since the sum of its digits (51) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (81985121521) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 217537 + ... + 459665.

It is an arithmetic number, because the mean of its divisors is an integer number (6951552300).

Almost surely, 2^81985121529 is an apocalyptic number.

It is an amenable number.

81985121529 is a deficient number, since it is larger than the sum of its proper divisors (29239715271).

81985121529 is a wasteful number, since it uses less digits than its factorization.

81985121529 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 244104.

The product of its digits is 518400, while the sum is 51.

The spelling of 81985121529 in words is "eighty-one billion, nine hundred eighty-five million, one hundred twenty-one thousand, five hundred twenty-nine".