21001221221 has 8 divisors (see below), whose sum is σ = 21716839584. Its totient is φ = 20297431440.

The previous prime is 21001221203. The next prime is 21001221229. The reversal of 21001221221 is 12212210012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21001221221 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001221196 and 21001221205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001221229) 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 7 ways as a sum of consecutive naturals, for example, 2953535 + ... + 2960636.

It is an arithmetic number, because the mean of its divisors is an integer number (2714604948).

Almost surely, 2^21001221221 is an apocalyptic number.

It is an amenable number.

21001221221 is a deficient number, since it is larger than the sum of its proper divisors (715618363).

21001221221 is an equidigital number, since it uses as much as digits as its factorization.

21001221221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5914291.

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

Adding to 21001221221 its reverse (12212210012), we get a palindrome (33213431233).

The spelling of 21001221221 in words is "twenty-one billion, one million, two hundred twenty-one thousand, two hundred twenty-one".