28918509 has 4 divisors (see below), whose sum is σ = 38558016. Its totient is φ = 19279004.

The previous prime is 28918501. The next prime is 28918511. The reversal of 28918509 is 90581982.

It is a happy number.

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 a cyclic number.

It is not a de Polignac number, because 28918509 - 2³ = 28918501 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28918501) 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, 4819749 + ... + 4819754.

It is an arithmetic number, because the mean of its divisors is an integer number (9639504).

Almost surely, 2^28918509 is an apocalyptic number.

It is an amenable number.

28918509 is a deficient number, since it is larger than the sum of its proper divisors (9639507).

28918509 is an equidigital number, since it uses as much as digits as its factorization.

28918509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9639506.

The product of its (nonzero) digits is 51840, while the sum is 42.

The square root of 28918509 is about 5377.5932348961. The cubic root of 28918509 is about 306.9436353850.

The spelling of 28918509 in words is "twenty-eight million, nine hundred eighteen thousand, five hundred nine".