21221211021 has 4 divisors (see below), whose sum is σ = 28294948032. Its totient is φ = 14147474012.

The previous prime is 21221211019. The next prime is 21221211043. The reversal of 21221211021 is 12011212212.

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 21221211021 - 2¹ = 21221211019 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221216021) 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, 3536868501 + ... + 3536868506.

It is an arithmetic number, because the mean of its divisors is an integer number (7073737008).

Almost surely, 2^21221211021 is an apocalyptic number.

It is an amenable number.

21221211021 is a deficient number, since it is larger than the sum of its proper divisors (7073737011).

21221211021 is an equidigital number, since it uses as much as digits as its factorization.

21221211021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7073737010.

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

Adding to 21221211021 its reverse (12011212212), we get a palindrome (33232423233).

The spelling of 21221211021 in words is "twenty-one billion, two hundred twenty-one million, two hundred eleven thousand, twenty-one".