21642165 has 12 divisors (see below), whose sum is σ = 37513164. Its totient is φ = 11542464.

The previous prime is 21642143. The next prime is 21642169. The reversal of 21642165 is 56124612.

21642165 is a `hidden beast` number, since 2 + 1 + 642 + 16 + 5 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 10929636 + 10712529 = 3306^2 + 3273^2 .

It is not a de Polignac number, because 21642165 - 2⁵ = 21642133 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 (21642169) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 240424 + ... + 240513.

It is an arithmetic number, because the mean of its divisors is an integer number (3126097).

Almost surely, 2^21642165 is an apocalyptic number.

It is an amenable number.

21642165 is a deficient number, since it is larger than the sum of its proper divisors (15870999).

21642165 is a wasteful number, since it uses less digits than its factorization.

21642165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 480948 (or 480945 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 21642165 is about 4652.1140355757. The cubic root of 21642165 is about 278.6764275927.

Adding to 21642165 its reverse (56124612), we get a palindrome (77766777).

The spelling of 21642165 in words is "twenty-one million, six hundred forty-two thousand, one hundred sixty-five".