81440165 has 4 divisors (see below), whose sum is σ = 97728204. Its totient is φ = 65152128.

The previous prime is 81440159. The next prime is 81440173. The reversal of 81440165 is 56104418.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 27520516 + 53919649 = 5246^2 + 7343^2 .

It is a cyclic number.

It is not a de Polignac number, because 81440165 - 2⁶ = 81440101 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 8144012 + ... + 8144021.

It is an arithmetic number, because the mean of its divisors is an integer number (24432051).

Almost surely, 2^81440165 is an apocalyptic number.

It is an amenable number.

81440165 is a deficient number, since it is larger than the sum of its proper divisors (16288039).

81440165 is a wasteful number, since it uses less digits than its factorization.

81440165 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16288038.

The product of its (nonzero) digits is 3840, while the sum is 29.

The square root of 81440165 is about 9024.4204800087. The cubic root of 81440165 is about 433.4571937190.

The spelling of 81440165 in words is "eighty-one million, four hundred forty thousand, one hundred sixty-five".