28689821 has 4 divisors (see below), whose sum is σ = 28775292. Its totient is φ = 28604352.

The previous prime is 28689811. The next prime is 28689823. The reversal of 28689821 is 12898682.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 5784025 + 22905796 = 2405^2 + 4786^2 .

It is a cyclic number.

It is not a de Polignac number, because 28689821 - 2¹⁸ = 28427677 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 (28689823) 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, 42230 + ... + 42903.

It is an arithmetic number, because the mean of its divisors is an integer number (7193823).

Almost surely, 2^28689821 is an apocalyptic number.

It is an amenable number.

28689821 is a deficient number, since it is larger than the sum of its proper divisors (85471).

28689821 is an equidigital number, since it uses as much as digits as its factorization.

28689821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 85470.

The product of its digits is 110592, while the sum is 44.

The square root of 28689821 is about 5356.2879870298. The cubic root of 28689821 is about 306.1323882133.

The spelling of 28689821 in words is "twenty-eight million, six hundred eighty-nine thousand, eight hundred twenty-one".