28457821 has 4 divisors (see below), whose sum is σ = 32523232. Its totient is φ = 24392412.

The previous prime is 28457797. The next prime is 28457833. The reversal of 28457821 is 12875482.

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 not a de Polignac number, because 28457821 - 2⁵ = 28457789 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28457851) 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, 2032695 + ... + 2032708.

It is an arithmetic number, because the mean of its divisors is an integer number (8130808).

Almost surely, 2^28457821 is an apocalyptic number.

It is an amenable number.

28457821 is a deficient number, since it is larger than the sum of its proper divisors (4065411).

28457821 is an equidigital number, since it uses as much as digits as its factorization.

28457821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4065410.

The product of its digits is 35840, while the sum is 37.

The square root of 28457821 is about 5334.5872380157. The cubic root of 28457821 is about 305.3049748912.

The spelling of 28457821 in words is "twenty-eight million, four hundred fifty-seven thousand, eight hundred twenty-one".