165805581 has 4 divisors (see below), whose sum is σ = 221074112. Its totient is φ = 110537052.

The previous prime is 165805579. The next prime is 165805583. The reversal of 165805581 is 185508561.

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 an interprime number because it is at equal distance from previous prime (165805579) and next prime (165805583).

It is not a de Polignac number, because 165805581 - 2¹ = 165805579 is a prime.

It is a super-2 number, since 2×165805581² = 54982981381495122, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165805583) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27634261 + ... + 27634266.

It is an arithmetic number, because the mean of its divisors is an integer number (55268528).

Almost surely, 2^165805581 is an apocalyptic number.

It is an amenable number.

165805581 is a deficient number, since it is larger than the sum of its proper divisors (55268531).

165805581 is an equidigital number, since it uses as much as digits as its factorization.

165805581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 55268530.

The product of its (nonzero) digits is 48000, while the sum is 39.

The square root of 165805581 is about 12876.5515958272. The cubic root of 165805581 is about 549.3718238559.

The spelling of 165805581 in words is "one hundred sixty-five million, eight hundred five thousand, five hundred eighty-one".