20406 has 16 divisors (see below), whose sum is σ = 43200. Its totient is φ = 6408.

The previous prime is 20399. The next prime is 20407. The reversal of 20406 is 60402.

It is a Curzon number.

It is a nialpdrome in base 12.

It is a junction number, because it is equal to n+sod(n) for n = 20391 and 20400.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20407) by changing a digit.

20406 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 7 ways as a sum of consecutive naturals, for example, 25 + ... + 203.

It is an arithmetic number, because the mean of its divisors is an integer number (2700).

2²⁰⁴⁰⁶ is an apocalyptic number.

20406 is an abundant number, since it is smaller than the sum of its proper divisors (22794).

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 (21600).

20406 is a wasteful number, since it uses less digits than its factorization.

20406 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 203.

The product of its (nonzero) digits is 48, while the sum is 12.

The square root of 20406 is about 142.8495712279. The cubic root of 20406 is about 27.3266227164.

Adding to 20406 its reverse (60402), we get a palindrome (80808).

The spelling of 20406 in words is "twenty thousand, four hundred six".