20405405 has 8 divisors (see below), whose sum is σ = 24739512. Its totient is φ = 16155648.

The previous prime is 20405387. The next prime is 20405443. The reversal of 20405405 is 50450402.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 2116 + 20403289 = 46^2 + 4517^2 .

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 20405405 - 2¹⁴ = 20389021 is a prime.

It is a Duffinian number.

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, 20552 + ... + 21521.

It is an arithmetic number, because the mean of its divisors is an integer number (3092439).

Almost surely, 2^20405405 is an apocalyptic number.

It is an amenable number.

20405405 is a deficient number, since it is larger than the sum of its proper divisors (4334107).

20405405 is an equidigital number, since it uses as much as digits as its factorization.

20405405 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 42175.

The product of its (nonzero) digits is 800, while the sum is 20.

The square root of 20405405 is about 4517.2342201839. The cubic root of 20405405 is about 273.2635711645.

Adding to 20405405 its reverse (50450402), we get a palindrome (70855807).

The spelling of 20405405 in words is "twenty million, four hundred five thousand, four hundred five".