28639 has 4 divisors (see below), whose sum is σ = 30856. Its totient is φ = 26424.

The previous prime is 28631. The next prime is 28643. The reversal of 28639 is 93682.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 28639 - 2³ = 28631 is a prime.

It is a Duffinian number.

28639 is a lucky number.

It is a nialpdrome in base 15.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28631) 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 3 ways as a sum of consecutive naturals, for example, 1089 + ... + 1114.

It is an arithmetic number, because the mean of its divisors is an integer number (7714).

2²⁸⁶³⁹ is an apocalyptic number.

28639 is a deficient number, since it is larger than the sum of its proper divisors (2217).

28639 is a wasteful number, since it uses less digits than its factorization.

28639 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2216.

The product of its digits is 2592, while the sum is 28.

The square root of 28639 is about 169.2306118880. The cubic root of 28639 is about 30.5951520934.

It can be divided in two parts, 286 and 39, that added together give a triangular number (325 = T₂₅).

The spelling of 28639 in words is "twenty-eight thousand, six hundred thirty-nine".