28640 has 24 divisors (see below), whose sum is σ = 68040. Its totient is φ = 11392.

The previous prime is 28631. The next prime is 28643. The reversal of 28640 is 4682.

It is a Harshad number since it is a multiple of its sum of digits (20).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28643) 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, 71 + ... + 249.

It is an arithmetic number, because the mean of its divisors is an integer number (2835).

2²⁸⁶⁴⁰ is an apocalyptic number.

28640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 28640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (34020).

28640 is an abundant number, since it is smaller than the sum of its proper divisors (39400).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

28640 is a wasteful number, since it uses less digits than its factorization.

28640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 194 (or 186 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 28640 is about 169.2335664104. The cubic root of 28640 is about 30.5955081905.

The spelling of 28640 in words is "twenty-eight thousand, six hundred forty".