28507309 has 4 divisors (see below), whose sum is σ = 28731904. Its totient is φ = 28282716.

The previous prime is 28507307. The next prime is 28507331. The reversal of 28507309 is 90370582.

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 an emirpimes, since its reverse is a distinct semiprime: 90370582 = 2 ⋅45185291.

It is a cyclic number.

It is not a de Polignac number, because 28507309 - 2¹ = 28507307 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28507307) 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, 112107 + ... + 112360.

It is an arithmetic number, because the mean of its divisors is an integer number (7182976).

Almost surely, 2^28507309 is an apocalyptic number.

It is an amenable number.

28507309 is a deficient number, since it is larger than the sum of its proper divisors (224595).

28507309 is a wasteful number, since it uses less digits than its factorization.

28507309 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 224594.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 28507309 is about 5339.2236327017. The cubic root of 28507309 is about 305.4818469824.

The spelling of 28507309 in words is "twenty-eight million, five hundred seven thousand, three hundred nine".