28708321 has 4 divisors (see below), whose sum is σ = 28724500. Its totient is φ = 28692144.

The previous prime is 28708319. The next prime is 28708327. The reversal of 28708321 is 12380782.

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 27878400 + 829921 = 5280^2 + 911^2 .

It is a cyclic number.

It is not a de Polignac number, because 28708321 - 2¹ = 28708319 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28708327) 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, 5046 + ... + 9103.

It is an arithmetic number, because the mean of its divisors is an integer number (7181125).

Almost surely, 2^28708321 is an apocalyptic number.

It is an amenable number.

28708321 is a deficient number, since it is larger than the sum of its proper divisors (16179).

28708321 is a wasteful number, since it uses less digits than its factorization.

28708321 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16178.

The product of its (nonzero) digits is 5376, while the sum is 31.

The square root of 28708321 is about 5358.0146509691. The cubic root of 28708321 is about 306.1981749872.

The spelling of 28708321 in words is "twenty-eight million, seven hundred eight thousand, three hundred twenty-one".