20518209268209 has 27 divisors (see below), whose sum is σ = 29704478879673. Its totient is φ = 13647922663752.

The previous prime is 20518209268187. The next prime is 20518209268229. The reversal of 20518209268209 is 90286290281502.

It is a happy number.

The square root of 20518209268209 is 4529703.

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

20518209268209 is a `hidden beast` number, since 2 + 0 + 518 + 20 + 9 + 26 + 82 + 0 + 9 = 666.

It is not a de Polignac number, because 20518209268209 - 2⁹ = 20518209267697 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20518209268229) by changing a digit.

It is a polite number, since it can be written in 26 ways as a sum of consecutive naturals, for example, 7107102564 + ... + 7107105450.

Almost surely, 2^{20518209268209} is an apocalyptic number.

20518209268209 is the 4529703-rd square number.

20518209268209 is the 2264852-nd centered octagonal number.

It is an amenable number.

20518209268209 is a deficient number, since it is larger than the sum of its proper divisors (9186269611464).

20518209268209 is an frugal number, since it uses more digits than its factorization.

20518209268209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6826 (or 3413 counting only the distinct ones).

The product of its (nonzero) digits is 2488320, while the sum is 54.

The spelling of 20518209268209 in words is "twenty trillion, five hundred eighteen billion, two hundred nine million, two hundred sixty-eight thousand, two hundred nine".