21201221221 has 4 divisors (see below), whose sum is σ = 22123013472. Its totient is φ = 20279428972.

The previous prime is 21201221207. The next prime is 21201221287. The reversal of 21201221221 is 12212210212.

It is a happy number.

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 21201221221 - 2⁵ = 21201221189 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21201221195 and 21201221204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201221291) 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, 460896091 + ... + 460896136.

It is an arithmetic number, because the mean of its divisors is an integer number (5530753368).

Almost surely, 2^21201221221 is an apocalyptic number.

It is an amenable number.

21201221221 is a deficient number, since it is larger than the sum of its proper divisors (921792251).

21201221221 is an equidigital number, since it uses as much as digits as its factorization.

21201221221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 921792250.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21201221221 its reverse (12212210212), we get a palindrome (33413431433).

The spelling of 21201221221 in words is "twenty-one billion, two hundred one million, two hundred twenty-one thousand, two hundred twenty-one".