21021021221 has 4 divisors (see below), whose sum is σ = 21021703200. Its totient is φ = 21020339244.

The previous prime is 21021021199. The next prime is 21021021269. The reversal of 21021021221 is 12212012012.

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 21021021221 - 2²² = 21016826917 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21021021196 and 21021021205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21021021821) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 292451 + ... + 357168.

It is an arithmetic number, because the mean of its divisors is an integer number (5255425800).

Almost surely, 2^21021021221 is an apocalyptic number.

It is an amenable number.

21021021221 is a deficient number, since it is larger than the sum of its proper divisors (681979).

21021021221 is an equidigital number, since it uses as much as digits as its factorization.

21021021221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 681978.

The product of its (nonzero) digits is 32, while the sum is 14.

Adding to 21021021221 its reverse (12212012012), we get a palindrome (33233033233).

The spelling of 21021021221 in words is "twenty-one billion, twenty-one million, twenty-one thousand, two hundred twenty-one".