20784 has 20 divisors (see below), whose sum is σ = 53816. Its totient is φ = 6912.

The previous prime is 20773. The next prime is 20789. The reversal of 20784 is 48702.

It is a happy number.

20784 is nontrivially palindromic in base 7.

It is a Smith number, since the sum of its digits (21) coincides with the sum of the digits of its prime factors.

It is a zygodrome in base 7.

It is a self number, because there is not a number n which added to its sum of digits gives 20784.

It is not an unprimeable number, because it can be changed into a prime (20789) 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, 169 + ... + 264.

2²⁰⁷⁸⁴ is an apocalyptic number.

20784 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

20784 is an abundant number, since it is smaller than the sum of its proper divisors (33032).

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 (26908).

20784 is a wasteful number, since it uses less digits than its factorization.

20784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 444 (or 438 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 21.

The square root of 20784 is about 144.1665703275. The cubic root of 20784 is about 27.4943238974.

The spelling of 20784 in words is "twenty thousand, seven hundred eighty-four".