165115561 has 16 divisors (see below), whose sum is σ = 181221264. Its totient is φ = 149520384.

The previous prime is 165115547. The next prime is 165115583. The reversal of 165115561 is 165511561.

It can be written as a sum of positive squares in 8 ways, for example, as 41216400 + 123899161 = 6420^2 + 11131^2 .

It is not a de Polignac number, because 165115561 - 2¹⁵ = 165082793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165115591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 243555 + ... + 244231.

It is an arithmetic number, because the mean of its divisors is an integer number (11326329).

Almost surely, 2^165115561 is an apocalyptic number.

It is an amenable number.

165115561 is a deficient number, since it is larger than the sum of its proper divisors (16105703).

165115561 is a wasteful number, since it uses less digits than its factorization.

165115561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1020.

The product of its digits is 4500, while the sum is 31.

The square root of 165115561 is about 12849.7299971634. The cubic root of 165115561 is about 548.6086717717.

The spelling of 165115561 in words is "one hundred sixty-five million, one hundred fifteen thousand, five hundred sixty-one".