21646161 has 12 divisors (see below), whose sum is σ = 31386420. Its totient is φ = 14375520.

The previous prime is 21646139. The next prime is 21646189. The reversal of 21646161 is 16164612.

21646161 is a `hidden beast` number, since 2 + 1 + 646 + 16 + 1 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 6969600 + 14676561 = 2640^2 + 3831^2 .

It is not a de Polignac number, because 21646161 - 2⁵ = 21646129 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21648161) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 2050 + ... + 6891.

It is an arithmetic number, because the mean of its divisors is an integer number (2615535).

Almost surely, 2^21646161 is an apocalyptic number.

It is an amenable number.

21646161 is a deficient number, since it is larger than the sum of its proper divisors (9740259).

21646161 is a wasteful number, since it uses less digits than its factorization.

21646161 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9216 (or 9213 counting only the distinct ones).

The product of its digits is 1728, while the sum is 27.

The square root of 21646161 is about 4652.5434979160. The cubic root of 21646161 is about 278.6935781023.

The spelling of 21646161 in words is "twenty-one million, six hundred forty-six thousand, one hundred sixty-one".