21111002221 has 4 divisors (see below), whose sum is σ = 21111449500. Its totient is φ = 21110554944.

The previous prime is 21111002219. The next prime is 21111002243. The reversal of 21111002221 is 12220011112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 8646396196 + 12464606025 = 92986^2 + 111645^2 .

It is a cyclic number.

It is not a de Polignac number, because 21111002221 - 2¹ = 21111002219 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21111002251) 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, 143196 + ... + 250453.

It is an arithmetic number, because the mean of its divisors is an integer number (5277862375).

Almost surely, 2^21111002221 is an apocalyptic number.

It is an amenable number.

21111002221 is a deficient number, since it is larger than the sum of its proper divisors (447279).

21111002221 is an equidigital number, since it uses as much as digits as its factorization.

21111002221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 447278.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21111002221 its reverse (12220011112), we get a palindrome (33331013333).

The spelling of 21111002221 in words is "twenty-one billion, one hundred eleven million, two thousand, two hundred twenty-one".