28381509 has 20 divisors (see below), whose sum is σ = 45660076. Its totient is φ = 17464896.

The previous prime is 28381453. The next prime is 28381511. The reversal of 28381509 is 90518382.

It can be written as a sum of positive squares in 2 ways, for example, as 11390625 + 16990884 = 3375^2 + 4122^2 .

It is not a de Polignac number, because 28381509 - 2⁸ = 28381253 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28381519) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 12424 + ... + 14529.

Almost surely, 2^28381509 is an apocalyptic number.

It is an amenable number.

28381509 is a deficient number, since it is larger than the sum of its proper divisors (17278567).

28381509 is a wasteful number, since it uses less digits than its factorization.

28381509 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 26978 (or 26969 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 28381509 is about 5327.4298681447. The cubic root of 28381509 is about 305.0318304144.

The spelling of 28381509 in words is "twenty-eight million, three hundred eighty-one thousand, five hundred nine".