21000022221 has 4 divisors (see below), whose sum is σ = 28000029632. Its totient is φ = 14000014812.

The previous prime is 21000022207. The next prime is 21000022229. The reversal of 21000022221 is 12222000012.

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 21000022221 - 2⁹ = 21000021709 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21000022197 and 21000022206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000022229) 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, 3500003701 + ... + 3500003706.

It is an arithmetic number, because the mean of its divisors is an integer number (7000007408).

Almost surely, 2^21000022221 is an apocalyptic number.

It is an amenable number.

21000022221 is a deficient number, since it is larger than the sum of its proper divisors (7000007411).

21000022221 is an equidigital number, since it uses as much as digits as its factorization.

21000022221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7000007410.

The product of its (nonzero) digits is 32, while the sum is 12.

Adding to 21000022221 its reverse (12222000012), we get a palindrome (33222022233).

It can be divided in two parts, 210000 and 22221, that added together give a triangular number (232221 = T₆₈₁).

The spelling of 21000022221 in words is "twenty-one billion, twenty-two thousand, two hundred twenty-one".