21102110221 has 4 divisors (see below), whose sum is σ = 21111065532. Its totient is φ = 21093154912.

The previous prime is 21102110203. The next prime is 21102110257. The reversal of 21102110221 is 12201120112.

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 10995829321 + 10106280900 = 104861^2 + 100530^2 .

It is a cyclic number.

It is not a de Polignac number, because 21102110221 - 2⁹ = 21102109709 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 (21102110021) 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, 4474120 + ... + 4478833.

It is an arithmetic number, because the mean of its divisors is an integer number (5277766383).

Almost surely, 2^21102110221 is an apocalyptic number.

It is an amenable number.

21102110221 is a deficient number, since it is larger than the sum of its proper divisors (8955311).

21102110221 is an equidigital number, since it uses as much as digits as its factorization.

21102110221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8955310.

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

Adding to 21102110221 its reverse (12201120112), we get a palindrome (33303230333).

The spelling of 21102110221 in words is "twenty-one billion, one hundred two million, one hundred ten thousand, two hundred twenty-one".