21013021221 has 16 divisors (see below), whose sum is σ = 28077798336. Its totient is φ = 13978498176.

The previous prime is 21013021201. The next prime is 21013021279. The reversal of 21013021221 is 12212031012.

It is not a de Polignac number, because 21013021221 - 2¹¹ = 21013019173 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21013021221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013021201) 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, 3049446 + ... + 3056328.

It is an arithmetic number, because the mean of its divisors is an integer number (1754862396).

Almost surely, 2^21013021221 is an apocalyptic number.

It is an amenable number.

21013021221 is a deficient number, since it is larger than the sum of its proper divisors (7064777115).

21013021221 is a wasteful number, since it uses less digits than its factorization.

21013021221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8932.

The product of its (nonzero) digits is 48, while the sum is 15.

Adding to 21013021221 its reverse (12212031012), we get a palindrome (33225052233).

The spelling of 21013021221 in words is "twenty-one billion, thirteen million, twenty-one thousand, two hundred twenty-one".