28320681 has 4 divisors (see below), whose sum is σ = 37760912. Its totient is φ = 18880452.

The previous prime is 28320671. The next prime is 28320683. The reversal of 28320681 is 18602382.

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 not a de Polignac number, because 28320681 - 2¹⁵ = 28287913 is a prime.

It is a super-2 number, since 2×28320681² = 1604121944607522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28320683) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4720111 + ... + 4720116.

It is an arithmetic number, because the mean of its divisors is an integer number (9440228).

Almost surely, 2^28320681 is an apocalyptic number.

It is an amenable number.

28320681 is a deficient number, since it is larger than the sum of its proper divisors (9440231).

28320681 is an equidigital number, since it uses as much as digits as its factorization.

28320681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9440230.

The product of its (nonzero) digits is 4608, while the sum is 30.

The square root of 28320681 is about 5321.7178617435. The cubic root of 28320681 is about 304.8137571205.

The spelling of 28320681 in words is "twenty-eight million, three hundred twenty thousand, six hundred eighty-one".