28704821 has 4 divisors (see below), whose sum is σ = 28750944. Its totient is φ = 28658700.

The previous prime is 28704811. The next prime is 28704883. The reversal of 28704821 is 12840782.

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, and also an emirpimes, since its reverse is a distinct semiprime: 12840782 = 2 ⋅6420391.

It is a cyclic number.

It is not a de Polignac number, because 28704821 - 2¹⁰ = 28703797 is a prime.

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 (28704811) 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, 22115 + ... + 23376.

It is an arithmetic number, because the mean of its divisors is an integer number (7187736).

Almost surely, 2^28704821 is an apocalyptic number.

It is an amenable number.

28704821 is a deficient number, since it is larger than the sum of its proper divisors (46123).

28704821 is an equidigital number, since it uses as much as digits as its factorization.

28704821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 46122.

The product of its (nonzero) digits is 7168, while the sum is 32.

The square root of 28704821 is about 5357.6880274984. The cubic root of 28704821 is about 306.1857310089.

The spelling of 28704821 in words is "twenty-eight million, seven hundred four thousand, eight hundred twenty-one".