28516821 has 4 divisors (see below), whose sum is σ = 38022432. Its totient is φ = 19011212.

The previous prime is 28516819. The next prime is 28516841. The reversal of 28516821 is 12861582.

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 28516821 - 2¹ = 28516819 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28516841) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4752801 + ... + 4752806.

It is an arithmetic number, because the mean of its divisors is an integer number (9505608).

Almost surely, 2^28516821 is an apocalyptic number.

It is an amenable number.

28516821 is a deficient number, since it is larger than the sum of its proper divisors (9505611).

28516821 is an equidigital number, since it uses as much as digits as its factorization.

28516821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9505610.

The product of its digits is 7680, while the sum is 33.

The square root of 28516821 is about 5340.1143246189. The cubic root of 28516821 is about 305.5158197927.

The spelling of 28516821 in words is "twenty-eight million, five hundred sixteen thousand, eight hundred twenty-one".