21000011221 has 4 divisors (see below), whose sum is σ = 24000012832. Its totient is φ = 18000009612.

The previous prime is 21000011173. The next prime is 21000011257. The reversal of 21000011221 is 12211000012.

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 21000011221 - 2¹⁵ = 20999978453 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21000011198 and 21000011207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000011281) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1500000795 + ... + 1500000808.

It is an arithmetic number, because the mean of its divisors is an integer number (6000003208).

Almost surely, 2^21000011221 is an apocalyptic number.

It is an amenable number.

21000011221 is a deficient number, since it is larger than the sum of its proper divisors (3000001611).

21000011221 is an equidigital number, since it uses as much as digits as its factorization.

21000011221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3000001610.

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21000011221 its reverse (12211000012), we get a palindrome (33211011233).

The spelling of 21000011221 in words is "twenty-one billion, eleven thousand, two hundred twenty-one".