81129285161 has 4 divisors (see below), whose sum is σ = 82106746512. Its totient is φ = 80151823812.

The previous prime is 81129285121. The next prime is 81129285179. The reversal of 81129285161 is 16158292118.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 81129285161 - 2²² = 81125090857 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (81129285121) 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 3 ways as a sum of consecutive naturals, for example, 488730551 + ... + 488730716.

It is an arithmetic number, because the mean of its divisors is an integer number (20526686628).

Almost surely, 2^81129285161 is an apocalyptic number.

It is an amenable number.

81129285161 is a deficient number, since it is larger than the sum of its proper divisors (977461351).

81129285161 is an equidigital number, since it uses as much as digits as its factorization.

81129285161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 977461350.

The product of its digits is 69120, while the sum is 44.

The spelling of 81129285161 in words is "eighty-one billion, one hundred twenty-nine million, two hundred eighty-five thousand, one hundred sixty-one".