165216321 has 8 divisors (see below), whose sum is σ = 244764960. Its totient is φ = 110144196.

The previous prime is 165216287. The next prime is 165216349. The reversal of 165216321 is 123612561.

165216321 is a `hidden beast` number, since 1 + 6 + 5 + 21 + 632 + 1 = 666.

It is not a de Polignac number, because 165216321 - 2⁷ = 165216193 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 6119123 = 165216321 / (1 + 6 + 5 + 2 + 1 + 6 + 3 + 2 + 1).

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

It is not an unprimeable number, because it can be changed into a prime (165216221) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3059535 + ... + 3059588.

It is an arithmetic number, because the mean of its divisors is an integer number (30595620).

Almost surely, 2^165216321 is an apocalyptic number.

It is an amenable number.

165216321 is a deficient number, since it is larger than the sum of its proper divisors (79548639).

165216321 is an equidigital number, since it uses as much as digits as its factorization.

165216321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6119132 (or 6119126 counting only the distinct ones).

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

The square root of 165216321 is about 12853.6501041533. The cubic root of 165216321 is about 548.7202432655.

Adding to 165216321 its reverse (123612561), we get a palindrome (288828882).

The spelling of 165216321 in words is "one hundred sixty-five million, two hundred sixteen thousand, three hundred twenty-one".