20640638980809 has 9 divisors (see below), whose sum is σ = 29814275992813. Its totient is φ = 13760416900812.

The previous prime is 20640638980757. The next prime is 20640638980849. The reversal of 20640638980809 is 90808983604602.

The square root of 20640638980809 is 4543197.

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

20640638980809 is a `hidden beast` number, since 206 + 40 + 6 + 389 + 8 + 0 + 8 + 0 + 9 = 666.

It is a tau number, because it is divible by the number of its divisors (9).

It is not a de Polignac number, because 20640638980809 - 2⁴³ = 11844545958601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20640638980849) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 12872392 + ... + 14386790.

Almost surely, 2^{20640638980809} is an apocalyptic number.

20640638980809 is the 4543197-th square number.

20640638980809 is the 2271599-th centered octagonal number.

It is an amenable number.

20640638980809 is a deficient number, since it is larger than the sum of its proper divisors (9173637012004).

20640638980809 is an frugal number, since it uses more digits than its factorization.

20640638980809 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3028804 (or 1514402 counting only the distinct ones).

The product of its (nonzero) digits is 35831808, while the sum is 63.

The spelling of 20640638980809 in words is "twenty trillion, six hundred forty billion, six hundred thirty-eight million, nine hundred eighty thousand, eight hundred nine".