28398509 has 4 divisors (see below), whose sum is σ = 28798560. Its totient is φ = 27998460.

The previous prime is 28398493. The next prime is 28398523. The reversal of 28398509 is 90589382.

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 28398509 - 2⁴ = 28398493 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 28398509.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28398809) 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, 199919 + ... + 200060.

It is an arithmetic number, because the mean of its divisors is an integer number (7199640).

Almost surely, 2^28398509 is an apocalyptic number.

It is an amenable number.

28398509 is a deficient number, since it is larger than the sum of its proper divisors (400051).

28398509 is an equidigital number, since it uses as much as digits as its factorization.

28398509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 400050.

The product of its (nonzero) digits is 155520, while the sum is 44.

The square root of 28398509 is about 5329.0251453713. The cubic root of 28398509 is about 305.0927210706.

The spelling of 28398509 in words is "twenty-eight million, three hundred ninety-eight thousand, five hundred nine".