165266561 has 4 divisors (see below), whose sum is σ = 168384852. Its totient is φ = 162148272.

The previous prime is 165266551. The next prime is 165266593. The reversal of 165266561 is 165662561.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 45144961 + 120121600 = 6719^2 + 10960^2 .

It is a cyclic number.

It is not a de Polignac number, because 165266561 - 2²² = 161072257 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (165266551) 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, 1559066 + ... + 1559171.

It is an arithmetic number, because the mean of its divisors is an integer number (42096213).

Almost surely, 2^165266561 is an apocalyptic number.

It is an amenable number.

165266561 is a deficient number, since it is larger than the sum of its proper divisors (3118291).

165266561 is an equidigital number, since it uses as much as digits as its factorization.

165266561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3118290.

The product of its digits is 64800, while the sum is 38.

The square root of 165266561 is about 12855.6042642888. The cubic root of 165266561 is about 548.7758570430.

The spelling of 165266561 in words is "one hundred sixty-five million, two hundred sixty-six thousand, five hundred sixty-one".