20405406 has 32 divisors (see below), whose sum is σ = 49386240. Its totient is φ = 5486976.

The previous prime is 20405387. The next prime is 20405443. The reversal of 20405406 is 60450402.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13576 + ... + 15003.

It is an arithmetic number, because the mean of its divisors is an integer number (1543320).

Almost surely, 2^20405406 is an apocalyptic number.

20405406 is an abundant number, since it is smaller than the sum of its proper divisors (28980834).

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

20405406 is a wasteful number, since it uses less digits than its factorization.

20405406 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 28608.

The product of its (nonzero) digits is 960, while the sum is 21.

The square root of 20405406 is about 4517.2343308710. The cubic root of 20405406 is about 273.2635756284.

Adding to 20405406 its reverse (60450402), we get a palindrome (80855808).

The spelling of 20405406 in words is "twenty million, four hundred five thousand, four hundred six".