21010211221 has 16 divisors (see below), whose sum is σ = 21436974000. Its totient is φ = 20588339200.

The previous prime is 21010211197. The next prime is 21010211227. The reversal of 21010211221 is 12211201012.

It can be written as a sum of positive squares in 8 ways, for example, as 629508100 + 20380703121 = 25090^2 + 142761^2 .

It is a cyclic number.

It is not a de Polignac number, because 21010211221 - 2¹³ = 21010203029 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 (21010211227) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6907461 + ... + 6910501.

It is an arithmetic number, because the mean of its divisors is an integer number (1339810875).

Almost surely, 2^21010211221 is an apocalyptic number.

It is an amenable number.

21010211221 is a deficient number, since it is larger than the sum of its proper divisors (426762779).

21010211221 is a wasteful number, since it uses less digits than its factorization.

21010211221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3800.

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

Adding to 21010211221 its reverse (12211201012), we get a palindrome (33221412233).

The spelling of 21010211221 in words is "twenty-one billion, ten million, two hundred eleven thousand, two hundred twenty-one".