21010211021 has 4 divisors (see below), whose sum is σ = 21119072412. Its totient is φ = 20901349632.

The previous prime is 21010211009. The next prime is 21010211041. The reversal of 21010211021 is 12011201012.

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 4017784996 + 16992426025 = 63386^2 + 130355^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21010211021 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21010210993 and 21010211011.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21010211041) 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, 54430406 + ... + 54430791.

It is an arithmetic number, because the mean of its divisors is an integer number (5279768103).

Almost surely, 2^21010211021 is an apocalyptic number.

It is an amenable number.

21010211021 is a deficient number, since it is larger than the sum of its proper divisors (108861391).

21010211021 is a wasteful number, since it uses less digits than its factorization.

21010211021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 108861390.

The product of its (nonzero) digits is 8, while the sum is 11.

Adding to 21010211021 its reverse (12011201012), we get a palindrome (33021412033).

The spelling of 21010211021 in words is "twenty-one billion, ten million, two hundred eleven thousand, twenty-one".