28638021 has 4 divisors (see below), whose sum is σ = 38184032. Its totient is φ = 19092012.

The previous prime is 28638019. The next prime is 28638061. The reversal of 28638021 is 12083682.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 28638021 - 2¹ = 28638019 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28638021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28638061) 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, 4773001 + ... + 4773006.

It is an arithmetic number, because the mean of its divisors is an integer number (9546008).

Almost surely, 2^28638021 is an apocalyptic number.

It is an amenable number.

28638021 is a deficient number, since it is larger than the sum of its proper divisors (9546011).

28638021 is an equidigital number, since it uses as much as digits as its factorization.

28638021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9546010.

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 28638021 is about 5351.4503641536. The cubic root of 28638021 is about 305.9480346632.

The spelling of 28638021 in words is "twenty-eight million, six hundred thirty-eight thousand, twenty-one".