43638021 has 20 divisors (see below), whose sum is σ = 74501152. Its totient is φ = 24935688.

The previous prime is 43637999. The next prime is 43638029. The reversal of 43638021 is 12083634.

It is a happy number.

43638021 is a `hidden beast` number, since 4 + 3 + 638 + 0 + 21 = 666.

43638021 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 43638021 - 2¹¹ = 43635973 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 Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (43638029) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 37915 + ... + 39048.

Almost surely, 2^43638021 is an apocalyptic number.

It is an amenable number.

43638021 is a deficient number, since it is larger than the sum of its proper divisors (30863131).

43638021 is an equidigital number, since it uses as much as digits as its factorization.

43638021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 76982 (or 76973 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 43638021 is about 6605.9080375070. The cubic root of 43638021 is about 352.0640513823.

The spelling of 43638021 in words is "forty-three million, six hundred thirty-eight thousand, twenty-one".