20664 has 48 divisors (see below), whose sum is σ = 65520. Its totient is φ = 5760.

The previous prime is 20663. The next prime is 20681. The reversal of 20664 is 46602.

20664 is a `hidden beast` number, since 2 + 0 + 664 = 666.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a nialpdrome in base 12 and base 14.

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 20664.

It is not an unprimeable number, because it can be changed into a prime (20663) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 484 + ... + 524.

It is an arithmetic number, because the mean of its divisors is an integer number (1365).

2²⁰⁶⁶⁴ is an apocalyptic number.

20664 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32760).

20664 is an abundant number, since it is smaller than the sum of its proper divisors (44856).

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

20664 is a wasteful number, since it uses less digits than its factorization.

20664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 60 (or 53 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 18.

The square root of 20664 is about 143.7497826085. The cubic root of 20664 is about 27.4413073295.

The spelling of 20664 in words is "twenty thousand, six hundred sixty-four".