21938165 has 4 divisors (see below), whose sum is σ = 26325804. Its totient is φ = 17550528.

The previous prime is 21938149. The next prime is 21938167. The reversal of 21938165 is 56183912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16072081 + 5866084 = 4009^2 + 2422^2 .

It is a cyclic number.

It is not a de Polignac number, because 21938165 - 2⁴ = 21938149 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21938167) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2193812 + ... + 2193821.

It is an arithmetic number, because the mean of its divisors is an integer number (6581451).

Almost surely, 2^21938165 is an apocalyptic number.

It is an amenable number.

21938165 is a deficient number, since it is larger than the sum of its proper divisors (4387639).

21938165 is an equidigital number, since it uses as much as digits as its factorization.

21938165 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4387638.

The product of its digits is 12960, while the sum is 35.

The square root of 21938165 is about 4683.8194884090. The cubic root of 21938165 is about 279.9411653594.

The spelling of 21938165 in words is "twenty-one million, nine hundred thirty-eight thousand, one hundred sixty-five".