165213621 has 16 divisors (see below), whose sum is σ = 251377600. Its totient is φ = 107164944.

The previous prime is 165213563. The next prime is 165213647. The reversal of 165213621 is 126312561.

165213621 is a `hidden beast` number, since 1 + 652 + 1 + 3 + 6 + 2 + 1 = 666.

It is not a de Polignac number, because 165213621 - 2¹¹ = 165211573 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (165213661) 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, 81691 + ... + 83688.

It is an arithmetic number, because the mean of its divisors is an integer number (15711100).

Almost surely, 2^165213621 is an apocalyptic number.

It is an amenable number.

165213621 is a deficient number, since it is larger than the sum of its proper divisors (86163979).

165213621 is a wasteful number, since it uses less digits than its factorization.

165213621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165425 (or 165419 counting only the distinct ones).

The product of its digits is 2160, while the sum is 27.

The square root of 165213621 is about 12853.5450751923. The cubic root of 165213621 is about 548.7172541485.

The spelling of 165213621 in words is "one hundred sixty-five million, two hundred thirteen thousand, six hundred twenty-one".