21210110210021 has 4 divisors (see below), whose sum is σ = 21227595875052. Its totient is φ = 21192624544992.

The previous prime is 21210110209993. The next prime is 21210110210027. The reversal of 21210110210021 is 12001201101212.

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 2964491932900 + 18245618277121 = 1721770^2 + 4271489^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21210110210021 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21210110209978 and 21210110210005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21210110210027) 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, 8742830696 + ... + 8742833121.

It is an arithmetic number, because the mean of its divisors is an integer number (5306898968763).

Almost surely, 2^{21210110210021} is an apocalyptic number.

It is an amenable number.

21210110210021 is a deficient number, since it is larger than the sum of its proper divisors (17485665031).

21210110210021 is a wasteful number, since it uses less digits than its factorization.

21210110210021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 17485665030.

The product of its (nonzero) digits is 16, while the sum is 14.

Adding to 21210110210021 its reverse (12001201101212), we get a palindrome (33211311311233).

The spelling of 21210110210021 in words is "twenty-one trillion, two hundred ten billion, one hundred ten million, two hundred ten thousand, twenty-one".