20006405 has 8 divisors (see below), whose sum is σ = 24228600. Its totient is φ = 15857856.

The previous prime is 20006359. The next prime is 20006419. The reversal of 20006405 is 50460002.

It can be written as a sum of positive squares in 4 ways, for example, as 2982529 + 17023876 = 1727^2 + 4126^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 20006405 - 2⁸ = 20006149 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17810 + ... + 18899.

It is an arithmetic number, because the mean of its divisors is an integer number (3028575).

Almost surely, 2^20006405 is an apocalyptic number.

It is an amenable number.

20006405 is a deficient number, since it is larger than the sum of its proper divisors (4222195).

20006405 is a wasteful number, since it uses less digits than its factorization.

20006405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36823.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 20006405 is about 4472.8519984457. The cubic root of 20006405 is about 271.4707349749.

Adding to 20006405 its reverse (50460002), we get a palindrome (70466407).

The spelling of 20006405 in words is "twenty million, six thousand, four hundred five".