21013351221 has 4 divisors (see below), whose sum is σ = 28017801632. Its totient is φ = 14008900812.

The previous prime is 21013351199. The next prime is 21013351231. The reversal of 21013351221 is 12215331012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21013351221 - 2²⁷ = 20879133493 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013351231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3502225201 + ... + 3502225206.

It is an arithmetic number, because the mean of its divisors is an integer number (7004450408).

Almost surely, 2^21013351221 is an apocalyptic number.

It is an amenable number.

21013351221 is a deficient number, since it is larger than the sum of its proper divisors (7004450411).

21013351221 is an equidigital number, since it uses as much as digits as its factorization.

21013351221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7004450410.

The product of its (nonzero) digits is 360, while the sum is 21.

Adding to 21013351221 its reverse (12215331012), we get a palindrome (33228682233).

The spelling of 21013351221 in words is "twenty-one billion, thirteen million, three hundred fifty-one thousand, two hundred twenty-one".