21121210221 has 4 divisors (see below), whose sum is σ = 28161613632. Its totient is φ = 14080806812.

The previous prime is 21121210171. The next prime is 21121210237. The reversal of 21121210221 is 12201212112.

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 21121210221 - 2¹⁴ = 21121193837 is a prime.

It is a super-2 number, since 2×21121210221² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21121210221.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121210421) 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, 3520201701 + ... + 3520201706.

It is an arithmetic number, because the mean of its divisors is an integer number (7040403408).

Almost surely, 2^21121210221 is an apocalyptic number.

It is an amenable number.

21121210221 is a deficient number, since it is larger than the sum of its proper divisors (7040403411).

21121210221 is an equidigital number, since it uses as much as digits as its factorization.

21121210221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7040403410.

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 21121210221 its reverse (12201212112), we get a palindrome (33322422333).

The spelling of 21121210221 in words is "twenty-one billion, one hundred twenty-one million, two hundred ten thousand, two hundred twenty-one".