20806 has 8 divisors (see below), whose sum is σ = 31824. Its totient is φ = 10200.

The previous prime is 20789. The next prime is 20807. The reversal of 20806 is 60802.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a self number, because there is not a number n which added to its sum of digits gives 20806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20807) 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, 151 + ... + 253.

It is an arithmetic number, because the mean of its divisors is an integer number (3978).

2²⁰⁸⁰⁶ is an apocalyptic number.

20806 is a deficient number, since it is larger than the sum of its proper divisors (11018).

20806 is a wasteful number, since it uses less digits than its factorization.

20806 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206.

The product of its (nonzero) digits is 96, while the sum is 16.

The square root of 20806 is about 144.2428507760. The cubic root of 20806 is about 27.5040214505.

Adding to 20806 its product of nonzero digits (96), we get a palindrome (20902).

The spelling of 20806 in words is "twenty thousand, eight hundred six".