20800 has 42 divisors (see below), whose sum is σ = 55118. Its totient is φ = 7680.

The previous prime is 20789. The next prime is 20807. The reversal of 20800 is 802.

It is a happy number.

It can be written as a sum of positive squares in 3 ways, for example, as 64 + 20736 = 8^2 + 144^2 .

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a super Niven number, because it is divisible the sum of any subset of its (nonzero) digits.

It is a plaindrome in base 11.

It is a nialpdrome in base 13.

It is a zygodrome in base 7.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20807) by changing a digit.

20800 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1594 + ... + 1606.

2²⁰⁸⁰⁰ is an apocalyptic number.

20800 is a gapful number since it is divisible by the number (20) 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 20800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27559).

20800 is an abundant number, since it is smaller than the sum of its proper divisors (34318).

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

20800 is a wasteful number, since it uses less digits than its factorization.

20800 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35 (or 20 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 10.

The square root of 20800 is about 144.2220510186. Note that the first 3 decimals coincide. The cubic root of 20800 is about 27.5013773415.

20800 divided by its sum of digits (10) gives a triangular number (2080 = T₆₄).

It can be divided in two parts, 20 and 800, that added together give a triangular number (820 = T₄₀).

The spelling of 20800 in words is "twenty thousand, eight hundred".