28405 has 16 divisors (see below), whose sum is σ = 40320. Its totient is φ = 19008.

The previous prime is 28403. The next prime is 28409. The reversal of 28405 is 50482.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 28405 - 2¹ = 28403 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

28405 is a lucky number.

It is a nialpdrome in base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (28403) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1224 + ... + 1246.

It is an arithmetic number, because the mean of its divisors is an integer number (2520).

2²⁸⁴⁰⁵ is an apocalyptic number.

It is an amenable number.

28405 is a deficient number, since it is larger than the sum of its proper divisors (11915).

28405 is a wasteful number, since it uses less digits than its factorization.

28405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 60.

The product of its (nonzero) digits is 320, while the sum is 19.

The square root of 28405 is about 168.5378295814. The cubic root of 28405 is about 30.5115964145.

Adding to 28405 its reverse (50482), we get a palindrome (78887).

The spelling of 28405 in words is "twenty-eight thousand, four hundred five".