165618181 has 4 divisors (see below), whose sum is σ = 165714412. Its totient is φ = 165521952.

The previous prime is 165618143. The next prime is 165618203. The reversal of 165618181 is 181816561.

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 81162081 + 84456100 = 9009^2 + 9190^2 .

It is a cyclic number.

It is not a de Polignac number, because 165618181 - 2¹⁷ = 165487109 is a prime.

It is a super-2 number, since 2×165618181² = 54858763755497522, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 165618181.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165618121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 45486 + ... + 48991.

It is an arithmetic number, because the mean of its divisors is an integer number (41428603).

Almost surely, 2^165618181 is an apocalyptic number.

It is an amenable number.

165618181 is a deficient number, since it is larger than the sum of its proper divisors (96231).

165618181 is an equidigital number, since it uses as much as digits as its factorization.

165618181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 96230.

The product of its digits is 11520, while the sum is 37.

The square root of 165618181 is about 12869.2727455750. The cubic root of 165618181 is about 549.1647719371.

It can be divided in two parts, 16561 and 8181, that added together give a palindrome (24742).

The spelling of 165618181 in words is "one hundred sixty-five million, six hundred eighteen thousand, one hundred eighty-one".