21000201221 has 4 divisors (see below), whose sum is σ = 21913253472. Its totient is φ = 20087148972.

The previous prime is 21000201217. The next prime is 21000201223. The reversal of 21000201221 is 12210200012.

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 21000201221 - 2² = 21000201217 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000201223) 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, 456526091 + ... + 456526136.

It is an arithmetic number, because the mean of its divisors is an integer number (5478313368).

Almost surely, 2^21000201221 is an apocalyptic number.

It is an amenable number.

21000201221 is a deficient number, since it is larger than the sum of its proper divisors (913052251).

21000201221 is an equidigital number, since it uses as much as digits as its factorization.

21000201221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 913052250.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21000201221 its reverse (12210200012), we get a palindrome (33210401233).

The spelling of 21000201221 in words is "twenty-one billion, two hundred one thousand, two hundred twenty-one".