28328821 has 2 divisors, whose sum is σ = 28328822. Its totient is φ = 28328820.

The previous prime is 28328819. The next prime is 28328831. The reversal of 28328821 is 12882382.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 27300625 + 1028196 = 5225^2 + 1014^2 .

It is a cyclic number.

It is not a de Polignac number, because 28328821 - 2¹ = 28328819 is a prime.

Together with 28328819, it forms a pair of twin primes.

It is equal to p_1760668 and since 28328821 and 1760668 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (28328831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 14164410 + 14164411.

It is an arithmetic number, because the mean of its divisors is an integer number (14164411).

Almost surely, 2^28328821 is an apocalyptic number.

It is an amenable number.

28328821 is a deficient number, since it is larger than the sum of its proper divisors (1).

28328821 is an equidigital number, since it uses as much as digits as its factorization.

28328821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12288, while the sum is 34.

The square root of 28328821 is about 5322.4825974351. The cubic root of 28328821 is about 304.8429577637.

The spelling of 28328821 in words is "twenty-eight million, three hundred twenty-eight thousand, eight hundred twenty-one".