21013355221 has 4 divisors (see below), whose sum is σ = 21013926444. Its totient is φ = 21012784000.

The previous prime is 21013355191. The next prime is 21013355249. The reversal of 21013355221 is 12255331012.

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 57608100 + 20955747121 = 7590^2 + 144761^2 .

It is a cyclic number.

It is not a de Polignac number, because 21013355221 - 2⁹ = 21013354709 is a prime.

It is a super-2 number, since 2×21013355221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013355521) 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, 226330 + ... + 305371.

It is an arithmetic number, because the mean of its divisors is an integer number (5253481611).

Almost surely, 2^21013355221 is an apocalyptic number.

It is an amenable number.

21013355221 is a deficient number, since it is larger than the sum of its proper divisors (571223).

21013355221 is an equidigital number, since it uses as much as digits as its factorization.

21013355221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 571222.

The product of its (nonzero) digits is 1800, while the sum is 25.

Adding to 21013355221 its reverse (12255331012), we get a palindrome (33268686233).

The spelling of 21013355221 in words is "twenty-one billion, thirteen million, three hundred fifty-five thousand, two hundred twenty-one".