28440 has 48 divisors (see below), whose sum is σ = 93600. Its totient is φ = 7488.

The previous prime is 28439. The next prime is 28447. The reversal of 28440 is 4482.

It is a happy number.

28440 is digitally balanced in base 4, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (18).

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 (28447) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 321 + ... + 399.

It is an arithmetic number, because the mean of its divisors is an integer number (1950).

2²⁸⁴⁴⁰ is an apocalyptic number.

28440 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 28440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (46800).

28440 is an abundant number, since it is smaller than the sum of its proper divisors (65160).

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

28440 is a wasteful number, since it uses less digits than its factorization.

28440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 96 (or 89 counting only the distinct ones).

The product of its (nonzero) digits is 256, while the sum is 18.

The square root of 28440 is about 168.6416318707. The cubic root of 28440 is about 30.5241231710.

It can be divided in two parts, 284 and 40, that added together give a square (324 = 18²).

The spelling of 28440 in words is "twenty-eight thousand, four hundred forty".