21594 has 16 divisors (see below), whose sum is σ = 44640. Its totient is φ = 6960.

The previous prime is 21589. The next prime is 21599. The reversal of 21594 is 49512.

21594 is nontrivially palindromic in base 11.

It is an interprime number because it is at equal distance from previous prime (21589) and next prime (21599).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21594.

It is not an unprimeable number, because it can be changed into a prime (21599) by changing a digit.

21594 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 (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 324 + ... + 384.

It is an arithmetic number, because the mean of its divisors is an integer number (2790).

2²¹⁵⁹⁴ is an apocalyptic number.

21594 is an abundant number, since it is smaller than the sum of its proper divisors (23046).

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

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22320).

21594 is a wasteful number, since it uses less digits than its factorization.

21594 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 125.

The product of its digits is 360, while the sum is 21.

The square root of 21594 is about 146.9489707347. The cubic root of 21594 is about 27.8469541024.

It can be divided in two parts, 2 and 1594, that added together give a triangular number (1596 = T₅₆).

The spelling of 21594 in words is "twenty-one thousand, five hundred ninety-four".