20505220136361 has 45 divisors (see below), whose sum is σ = 30743009841621. Its totient is φ = 13620453533568.

The previous prime is 20505220136333. The next prime is 20505220136363. The reversal of 20505220136361 is 16363102250502.

The square root of 20505220136361 is 4528269.

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

20505220136361 is a `hidden beast` number, since 2 + 0 + 5 + 0 + 5 + 2 + 2 + 0 + 13 + 636 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 669420148761 + 19835799987600 = 818181^2 + 4453740^2 .

It is not a de Polignac number, because 20505220136361 - 2⁵ = 20505220136329 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20505220136363) by changing a digit.

It is a polite number, since it can be written in 44 ways as a sum of consecutive naturals, for example, 13734239131 + ... + 13734240623.

Almost surely, 2^{20505220136361} is an apocalyptic number.

20505220136361 is the 4528269-th square number.

20505220136361 is the 2264135-th centered octagonal number.

It is an amenable number.

20505220136361 is a deficient number, since it is larger than the sum of its proper divisors (10237789705260).

20505220136361 is an frugal number, since it uses more digits than its factorization.

20505220136361 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3672 (or 1833 counting only the distinct ones).

The product of its (nonzero) digits is 64800, while the sum is 36.

Multiplying 20505220136361 by its sum of digits (36), we get a square (738187924908996 = 27169614²).

Adding to 20505220136361 its reverse (16363102250502), we get a palindrome (36868322386863).

The spelling of 20505220136361 in words is "twenty trillion, five hundred five billion, two hundred twenty million, one hundred thirty-six thousand, three hundred sixty-one".