21013210212221 has 4 divisors (see below), whose sum is σ = 21028649750844. Its totient is φ = 20997770673600.

The previous prime is 21013210212149. The next prime is 21013210212251. The reversal of 21013210212221 is 12221201231012.

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 4532768740900 + 16480441471321 = 2129030^2 + 4059611^2 .

It is a cyclic number.

It is not a de Polignac number, because 21013210212221 - 2¹⁴ = 21013210195837 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21013210212193 and 21013210212202.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21013210212251) 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, 7719767270 + ... + 7719769991.

It is an arithmetic number, because the mean of its divisors is an integer number (5257162437711).

Almost surely, 2^{21013210212221} is an apocalyptic number.

It is an amenable number.

21013210212221 is a deficient number, since it is larger than the sum of its proper divisors (15439538623).

21013210212221 is a wasteful number, since it uses less digits than its factorization.

21013210212221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15439538622.

The product of its (nonzero) digits is 192, while the sum is 20.

Adding to 21013210212221 its reverse (12221201231012), we get a palindrome (33234411443233).

The spelling of 21013210212221 in words is "twenty-one trillion, thirteen billion, two hundred ten million, two hundred twelve thousand, two hundred twenty-one".