20405265409 has 9 divisors (see below), whose sum is σ = 20532760131. Its totient is φ = 20278560120.

The previous prime is 20405265379. The next prime is 20405265437. The reversal of 20405265409 is 90456250402.

The square root of 20405265409 is 142847.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 20284880625 + 120384784 = 142425^2 + 10972^2 .

It is not a de Polignac number, because 20405265409 - 2³¹ = 18257781761 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20405265449) 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 8 ways as a sum of consecutive naturals, for example, 30140379 + ... + 30141055.

Almost surely, 2^20405265409 is an apocalyptic number.

20405265409 is the 142847-th square number.

20405265409 is the 71424-th centered octagonal number.

It is an amenable number.

20405265409 is a deficient number, since it is larger than the sum of its proper divisors (127494722).

20405265409 is an frugal number, since it uses more digits than its factorization.

20405265409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1776 (or 888 counting only the distinct ones).

The product of its (nonzero) digits is 86400, while the sum is 37.

The spelling of 20405265409 in words is "twenty billion, four hundred five million, two hundred sixty-five thousand, four hundred nine".