81181605165 has 16 divisors (see below), whose sum is σ = 132654198528. Its totient is φ = 42375646016.

The previous prime is 81181605139. The next prime is 81181605181. The reversal of 81181605165 is 56150618118.

It is a cyclic number.

It is not a de Polignac number, because 81181605165 - 2⁸ = 81181604909 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 57574902 + ... + 57576311.

It is an arithmetic number, because the mean of its divisors is an integer number (8290887408).

Almost surely, 2^81181605165 is an apocalyptic number.

It is an amenable number.

81181605165 is a deficient number, since it is larger than the sum of its proper divisors (51472593363).

81181605165 is a wasteful number, since it uses less digits than its factorization.

81181605165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115151268.

The product of its (nonzero) digits is 57600, while the sum is 42.

The spelling of 81181605165 in words is "eighty-one billion, one hundred eighty-one million, six hundred five thousand, one hundred sixty-five".