20785 has 4 divisors (see below), whose sum is σ = 24948. Its totient is φ = 16624.

The previous prime is 20773. The next prime is 20789. The reversal of 20785 is 58702.

20785 = 41² + 42² + ... + 50².

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8464 + 12321 = 92^2 + 111^2 .

It is a cyclic number.

It is not a de Polignac number, because 20785 - 2⁵ = 20753 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an Ulam number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20789) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2074 + ... + 2083.

It is an arithmetic number, because the mean of its divisors is an integer number (6237).

2²⁰⁷⁸⁵ is an apocalyptic number.

It is an amenable number.

20785 is a deficient number, since it is larger than the sum of its proper divisors (4163).

20785 is an equidigital number, since it uses as much as digits as its factorization.

20785 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4162.

The product of its (nonzero) digits is 560, while the sum is 22.

The square root of 20785 is about 144.1700384962. The cubic root of 20785 is about 27.4947648437.

It can be divided in two parts, 207 and 85, that added together give a palindrome (292).

The spelling of 20785 in words is "twenty thousand, seven hundred eighty-five".