21534 has 16 divisors (see below), whose sum is σ = 44688. Its totient is φ = 6912.

The previous prime is 21529. The next prime is 21557. The reversal of 21534 is 43512.

It is a congruent number.

It is an unprimeable 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, 174 + ... + 270.

It is an arithmetic number, because the mean of its divisors is an integer number (2793).

2²¹⁵³⁴ is an apocalyptic number.

21534 is an abundant number, since it is smaller than the sum of its proper divisors (23154).

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 (22344).

21534 is a wasteful number, since it uses less digits than its factorization.

21534 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 139.

The product of its digits is 120, while the sum is 15.

The square root of 21534 is about 146.7446762237. The cubic root of 21534 is about 27.8211387969.

It can be divided in two parts, 21 and 534, that added together give a palindrome (555).

The spelling of 21534 in words is "twenty-one thousand, five hundred thirty-four".