20688 has 20 divisors (see below), whose sum is σ = 53568. Its totient is φ = 6880.

The previous prime is 20681. The next prime is 20693. The reversal of 20688 is 88602.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a plaindrome in base 14.

It is a nialpdrome in base 12 and base 13.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20681) by changing a digit.

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, 168 + ... + 263.

2²⁰⁶⁸⁸ is an apocalyptic number.

It is an amenable number.

20688 is an abundant number, since it is smaller than the sum of its proper divisors (32880).

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 (26784).

20688 is a wasteful number, since it uses less digits than its factorization.

20688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 442 (or 436 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 24.

The square root of 20688 is about 143.8332367709. The cubic root of 20688 is about 27.4519270315.

The spelling of 20688 in words is "twenty thousand, six hundred eighty-eight".