165428508581 has 4 divisors (see below), whose sum is σ = 189061152672. Its totient is φ = 141795864492.

The previous prime is 165428508559. The next prime is 165428508589. The reversal of 165428508581 is 185805824561.

165428508581 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 165428508581 - 2²² = 165424314277 is a prime.

It is a super-2 number, since 2×165428508581² (a number of 23 digits) contains 22 as substring.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165428508589) 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, 11816322035 + ... + 11816322048.

It is an arithmetic number, because the mean of its divisors is an integer number (47265288168).

Almost surely, 2^165428508581 is an apocalyptic number.

It is an amenable number.

165428508581 is a deficient number, since it is larger than the sum of its proper divisors (23632644091).

165428508581 is an equidigital number, since it uses as much as digits as its factorization.

165428508581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23632644090.

The product of its (nonzero) digits is 3072000, while the sum is 53.

The spelling of 165428508581 in words is "one hundred sixty-five billion, four hundred twenty-eight million, five hundred eight thousand, five hundred eighty-one".