28715809 has 4 divisors (see below), whose sum is σ = 28728000. Its totient is φ = 28703620.

The previous prime is 28715807. The next prime is 28715833. The reversal of 28715809 is 90851782.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 28715809 - 2¹ = 28715807 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (28715803) 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, 1309 + ... + 7690.

It is an arithmetic number, because the mean of its divisors is an integer number (7182000).

Almost surely, 2^28715809 is an apocalyptic number.

It is an amenable number.

28715809 is a deficient number, since it is larger than the sum of its proper divisors (12191).

28715809 is an equidigital number, since it uses as much as digits as its factorization.

28715809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12190.

The product of its (nonzero) digits is 40320, while the sum is 40.

The square root of 28715809 is about 5358.7133716966. The cubic root of 28715809 is about 306.2247945936.

The spelling of 28715809 in words is "twenty-eight million, seven hundred fifteen thousand, eight hundred nine".