28891509 has 4 divisors (see below), whose sum is σ = 38522016. Its totient is φ = 19261004.

The previous prime is 28891507. The next prime is 28891529. The reversal of 28891509 is 90519882.

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 28891509 - 2¹ = 28891507 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28891507) 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, 4815249 + ... + 4815254.

It is an arithmetic number, because the mean of its divisors is an integer number (9630504).

Almost surely, 2^28891509 is an apocalyptic number.

It is an amenable number.

28891509 is a deficient number, since it is larger than the sum of its proper divisors (9630507).

28891509 is an equidigital number, since it uses as much as digits as its factorization.

28891509 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9630506.

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

The square root of 28891509 is about 5375.0822319291. The cubic root of 28891509 is about 306.8480788365.

The spelling of 28891509 in words is "twenty-eight million, eight hundred ninety-one thousand, five hundred nine".