165515561 has 2 divisors, whose sum is σ = 165515562. Its totient is φ = 165515560.

The previous prime is 165515531. The next prime is 165515563.

165515561 is nontrivially palindromic in base 10.

165515561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 163968025 + 1547536 = 12805^2 + 1244^2 .

It is a palprime.

It is a cyclic number.

It is not a de Polignac number, because 165515561 - 2¹⁰ = 165514537 is a prime.

Together with 165515563, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (165515563) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 82757780 + 82757781.

It is an arithmetic number, because the mean of its divisors is an integer number (82757781).

Almost surely, 2^165515561 is an apocalyptic number.

It is an amenable number.

165515561 is a deficient number, since it is larger than the sum of its proper divisors (1).

165515561 is an equidigital number, since it uses as much as digits as its factorization.

165515561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 22500, while the sum is 35.

The square root of 165515561 is about 12865.2851114929. The cubic root of 165515561 is about 549.0513243833.

The spelling of 165515561 in words is "one hundred sixty-five million, five hundred fifteen thousand, five hundred sixty-one".