28509639 has 24 divisors (see below), whose sum is σ = 40466160. Its totient is φ = 17829504.

The previous prime is 28509619. The next prime is 28509659. The reversal of 28509639 is 93690582.

It is an interprime number because it is at equal distance from previous prime (28509619) and next prime (28509659).

It is not a de Polignac number, because 28509639 - 2¹⁵ = 28476871 is a prime.

It is a super-3 number, since 3×28509639³ (a number of 23 digits) contains 333 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 28509639.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28509619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 390507 + ... + 390579.

It is an arithmetic number, because the mean of its divisors is an integer number (1686090).

Almost surely, 2^28509639 is an apocalyptic number.

28509639 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

28509639 is a deficient number, since it is larger than the sum of its proper divisors (11956521).

28509639 is an equidigital number, since it uses as much as digits as its factorization.

28509639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 239 (or 172 counting only the distinct ones).

The product of its (nonzero) digits is 116640, while the sum is 42.

The square root of 28509639 is about 5339.4418247603. The cubic root of 28509639 is about 305.4901694482.

The spelling of 28509639 in words is "twenty-eight million, five hundred nine thousand, six hundred thirty-nine".