165531213 has 6 divisors (see below), whose sum is σ = 239100654. Its totient is φ = 110354136.

The previous prime is 165531203. The next prime is 165531241. The reversal of 165531213 is 312135561.

165531213 is a `hidden beast` number, since 1 + 655 + 3 + 1 + 2 + 1 + 3 = 666.

It can be written as a sum of positive squares in only one way, i.e., 134861769 + 30669444 = 11613^2 + 5538^2 .

It is a de Polignac number, because none of the positive numbers 2^k-165531213 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165531203) 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 5 ways as a sum of consecutive naturals, for example, 9196170 + ... + 9196187.

It is an arithmetic number, because the mean of its divisors is an integer number (39850109).

Almost surely, 2^165531213 is an apocalyptic number.

It is an amenable number.

165531213 is a deficient number, since it is larger than the sum of its proper divisors (73569441).

165531213 is a wasteful number, since it uses less digits than its factorization.

165531213 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18392363 (or 18392360 counting only the distinct ones).

The product of its digits is 2700, while the sum is 27.

The square root of 165531213 is about 12865.8934007709. The cubic root of 165531213 is about 549.0686308738.

Adding to 165531213 its reverse (312135561), we get a palindrome (477666774).

It can be divided in two parts, 16553 and 1213, that added together give a triangular number (17766 = T₁₈₈).

The spelling of 165531213 in words is "one hundred sixty-five million, five hundred thirty-one thousand, two hundred thirteen".