21221221021 has 16 divisors (see below), whose sum is σ = 28492829568. Its totient is φ = 15264014400.

The previous prime is 21221220997. The next prime is 21221221039. The reversal of 21221221021 is 12012212212.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21221221021 - 2⁹ = 21221220509 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21221220986 and 21221221004.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221221061) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 10599010 + ... + 10601011.

It is an arithmetic number, because the mean of its divisors is an integer number (1780801848).

Almost surely, 2^21221221021 is an apocalyptic number.

It is an amenable number.

21221221021 is a deficient number, since it is larger than the sum of its proper divisors (7271608547).

21221221021 is a wasteful number, since it uses less digits than its factorization.

21221221021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21200052.

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

Adding to 21221221021 its reverse (12012212212), we get a palindrome (33233433233).

It can be divided in two parts, 21221 and 221021, that added together give a palindrome (242242).

The spelling of 21221221021 in words is "twenty-one billion, two hundred twenty-one million, two hundred twenty-one thousand, twenty-one".