21001322221 has 16 divisors (see below), whose sum is σ = 23405776128. Its totient is φ = 18679680000.

The previous prime is 21001322219. The next prime is 21001322261. The reversal of 21001322221 is 12222310012.

It is a happy number.

It is not a de Polignac number, because 21001322221 - 2¹ = 21001322219 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001322195 and 21001322204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001322201) 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, 2328721 + ... + 2337721.

It is an arithmetic number, because the mean of its divisors is an integer number (1462861008).

Almost surely, 2^21001322221 is an apocalyptic number.

It is an amenable number.

21001322221 is a deficient number, since it is larger than the sum of its proper divisors (2404453907).

21001322221 is a wasteful number, since it uses less digits than its factorization.

21001322221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13572.

The product of its (nonzero) digits is 96, while the sum is 16.

Adding to 21001322221 its reverse (12222310012), we get a palindrome (33223632233).

The spelling of 21001322221 in words is "twenty-one billion, one million, three hundred twenty-two thousand, two hundred twenty-one".