20205221521 has 4 divisors (see below), whose sum is σ = 20698031844. Its totient is φ = 19712411200.

The previous prime is 20205221513. The next prime is 20205221527. The reversal of 20205221521 is 12512250202.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8097300225 + 12107921296 = 89985^2 + 110036^2 .

It is a cyclic number.

It is not a de Polignac number, because 20205221521 - 2³ = 20205221513 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20205221492 and 20205221501.

It is not an unprimeable number, because it can be changed into a prime (20205221527) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 246405100 + ... + 246405181.

It is an arithmetic number, because the mean of its divisors is an integer number (5174507961).

Almost surely, 2^20205221521 is an apocalyptic number.

It is an amenable number.

20205221521 is a deficient number, since it is larger than the sum of its proper divisors (492810323).

20205221521 is an equidigital number, since it uses as much as digits as its factorization.

20205221521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 492810322.

The product of its (nonzero) digits is 800, while the sum is 22.

Adding to 20205221521 its reverse (12512250202), we get a palindrome (32717471723).

The spelling of 20205221521 in words is "twenty billion, two hundred five million, two hundred twenty-one thousand, five hundred twenty-one".