28288421 has 4 divisors (see below), whose sum is σ = 32329632. Its totient is φ = 24247212.

The previous prime is 28288411. The next prime is 28288433. The reversal of 28288421 is 12488282.

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 a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-28288421 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 (28288411) 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, 2020595 + ... + 2020608.

It is an arithmetic number, because the mean of its divisors is an integer number (8082408).

Almost surely, 2^28288421 is an apocalyptic number.

It is an amenable number.

28288421 is a deficient number, since it is larger than the sum of its proper divisors (4041211).

28288421 is an equidigital number, since it uses as much as digits as its factorization.

28288421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4041210.

The product of its digits is 16384, while the sum is 35.

The square root of 28288421 is about 5318.6860219419. The cubic root of 28288421 is about 304.6979756784.

The spelling of 28288421 in words is "twenty-eight million, two hundred eighty-eight thousand, four hundred twenty-one".