21012220221 has 4 divisors (see below), whose sum is σ = 28016293632. Its totient is φ = 14008146812.

The previous prime is 21012220211. The next prime is 21012220223. The reversal of 21012220221 is 12202221012.

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 a cyclic number.

It is not a de Polignac number, because 21012220221 - 2¹⁰ = 21012219197 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21012220221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012220223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3502036701 + ... + 3502036706.

It is an arithmetic number, because the mean of its divisors is an integer number (7004073408).

Almost surely, 2^21012220221 is an apocalyptic number.

It is an amenable number.

21012220221 is a deficient number, since it is larger than the sum of its proper divisors (7004073411).

21012220221 is an equidigital number, since it uses as much as digits as its factorization.

21012220221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7004073410.

The product of its (nonzero) digits is 64, while the sum is 15.

Adding to 21012220221 its reverse (12202221012), we get a palindrome (33214441233).

The spelling of 21012220221 in words is "twenty-one billion, twelve million, two hundred twenty thousand, two hundred twenty-one".