20864 has 16 divisors (see below), whose sum is σ = 41820. Its totient is φ = 10368.

The previous prime is 20857. The next prime is 20873. The reversal of 20864 is 46802.

It is a tau number, because it is divible by the number of its divisors (16).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 47 + ... + 209.

2²⁰⁸⁶⁴ 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 20864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (20910).

20864 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

20864 is an equidigital number, since it uses as much as digits as its factorization.

20864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 177 (or 165 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 20.

The square root of 20864 is about 144.4437606821. The cubic root of 20864 is about 27.5295550019.

It can be divided in two parts, 208 and 64, that added together give a palindrome (272).

The spelling of 20864 in words is "twenty thousand, eight hundred sixty-four".