21584 has 20 divisors (see below), whose sum is σ = 44640. Its totient is φ = 10080.

The previous prime is 21577. The next prime is 21587. The reversal of 21584 is 48512.

It is a hoax number, since the sum of its digits (20) coincides with the sum of the digits of its distinct prime factors.

It is an Ulam number.

It is a zygodrome in base 7.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21584.

It is not an unprimeable number, because it can be changed into a prime (21587) by changing a digit.

21584 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 269 + ... + 339.

It is an arithmetic number, because the mean of its divisors is an integer number (2232).

2²¹⁵⁸⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21584, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22320).

21584 is an abundant number, since it is smaller than the sum of its proper divisors (23056).

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

21584 is a wasteful number, since it uses less digits than its factorization.

21584 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 98 (or 92 counting only the distinct ones).

The product of its digits is 320, while the sum is 20.

The square root of 21584 is about 146.9149413777. The cubic root of 21584 is about 27.8426548752.

Adding to 21584 its product of digits (320), we get a square (21904 = 148²).

The spelling of 21584 in words is "twenty-one thousand, five hundred eighty-four".