28004421 has 4 divisors (see below), whose sum is σ = 37339232. Its totient is φ = 18669612.

The previous prime is 28004419. The next prime is 28004437. The reversal of 28004421 is 12440082.

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 28004421 - 2¹ = 28004419 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 (28004021) 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 3 ways as a sum of consecutive naturals, for example, 4667401 + ... + 4667406.

It is an arithmetic number, because the mean of its divisors is an integer number (9334808).

Almost surely, 2^28004421 is an apocalyptic number.

It is an amenable number.

28004421 is a deficient number, since it is larger than the sum of its proper divisors (9334811).

28004421 is an equidigital number, since it uses as much as digits as its factorization.

28004421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9334810.

The product of its (nonzero) digits is 512, while the sum is 21.

The square root of 28004421 is about 5291.9203508745. The cubic root of 28004421 is about 303.6748782035.

The spelling of 28004421 in words is "twenty-eight million, four thousand, four hundred twenty-one".