165820581 has 32 divisors (see below), whose sum is σ = 266956800. Its totient is φ = 101340720.

The previous prime is 165820573. The next prime is 165820591. The reversal of 165820581 is 185028561.

165820581 is a `hidden beast` number, since 1 + 6 + 58 + 20 + 581 = 666.

It is not a de Polignac number, because 165820581 - 2³ = 165820573 is a prime.

It is a super-2 number, since 2×165820581² = 54992930166355122, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165820541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 10690 + ... + 21116.

It is an arithmetic number, because the mean of its divisors is an integer number (8342400).

Almost surely, 2^165820581 is an apocalyptic number.

It is an amenable number.

165820581 is a deficient number, since it is larger than the sum of its proper divisors (101136219).

165820581 is a wasteful number, since it uses less digits than its factorization.

165820581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10486 (or 10480 counting only the distinct ones).

The product of its (nonzero) digits is 19200, while the sum is 36.

The square root of 165820581 is about 12877.1340367335. The cubic root of 165820581 is about 549.3883901033.

The spelling of 165820581 in words is "one hundred sixty-five million, eight hundred twenty thousand, five hundred eighty-one".