20405409 has 16 divisors (see below), whose sum is σ = 28214784. Its totient is φ = 13104000.

The previous prime is 20405387. The next prime is 20405443. The reversal of 20405409 is 90450402.

It is not a de Polignac number, because 20405409 - 2⁸ = 20405153 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20405459) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28759 + ... + 29459.

It is an arithmetic number, because the mean of its divisors is an integer number (1763424).

Almost surely, 2^20405409 is an apocalyptic number.

It is an amenable number.

20405409 is a deficient number, since it is larger than the sum of its proper divisors (7809375).

20405409 is a wasteful number, since it uses less digits than its factorization.

20405409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1048.

The product of its (nonzero) digits is 1440, while the sum is 24.

The square root of 20405409 is about 4517.2346629326. The cubic root of 20405409 is about 273.2635890201.

The spelling of 20405409 in words is "twenty million, four hundred five thousand, four hundred nine".