165561 has 16 divisors (see below), whose sum is σ = 250560. Its totient is φ = 96320.

The previous prime is 165559. The next prime is 165569.

165561 is nontrivially palindromic in base 10.

165561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a cyclic number.

It is not a de Polignac number, because 165561 - 2¹ = 165559 is a prime.

It is a plaindrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (165569) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 871 + ... + 1043.

It is an arithmetic number, because the mean of its divisors is an integer number (15660).

2¹⁶⁵⁵⁶¹ is an apocalyptic number.

165561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

165561 is a deficient number, since it is larger than the sum of its proper divisors (84999).

165561 is a wasteful number, since it uses less digits than its factorization.

165561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 216.

The product of its digits is 900, while the sum is 24.

The square root of 165561 is about 406.8918775301. The cubic root of 165561 is about 54.9101563487.

The spelling of 165561 in words is "one hundred sixty-five thousand, five hundred sixty-one".