21013311221 has 16 divisors (see below), whose sum is σ = 25110902784. Its totient is φ = 17192864304.

The previous prime is 21013311211. The next prime is 21013311233. The reversal of 21013311221 is 12211331012.

It is a de Polignac number, because none of the positive numbers 2^k-21013311221 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21013311221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013311211) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 55595 + ... + 212408.

It is an arithmetic number, because the mean of its divisors is an integer number (1569431424).

Almost surely, 2^21013311221 is an apocalyptic number.

It is an amenable number.

21013311221 is a deficient number, since it is larger than the sum of its proper divisors (4097591563).

21013311221 is a wasteful number, since it uses less digits than its factorization.

21013311221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 268520.

The product of its (nonzero) digits is 72, while the sum is 17.

Adding to 21013311221 its reverse (12211331012), we get a palindrome (33224642233).

The spelling of 21013311221 in words is "twenty-one billion, thirteen million, three hundred eleven thousand, two hundred twenty-one".