21102202021 has 4 divisors (see below), whose sum is σ = 21102511500. Its totient is φ = 21101892544.

The previous prime is 21102202007. The next prime is 21102202073. The reversal of 21102202021 is 12020220112.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 19241573796 + 1860628225 = 138714^2 + 43135^2 .

It is a cyclic number.

It is not a de Polignac number, because 21102202021 - 2¹⁷ = 21102070949 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21102201992 and 21102202010.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21102202091) 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, 2596 + ... + 205453.

It is an arithmetic number, because the mean of its divisors is an integer number (5275627875).

Almost surely, 2^21102202021 is an apocalyptic number.

It is an amenable number.

21102202021 is a deficient number, since it is larger than the sum of its proper divisors (309479).

21102202021 is a wasteful number, since it uses less digits than its factorization.

21102202021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 309478.

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 21102202021 its reverse (12020220112), we get a palindrome (33122422133).

The spelling of 21102202021 in words is "twenty-one billion, one hundred two million, two hundred two thousand, twenty-one".