21012010021 has 16 divisors (see below), whose sum is σ = 21564797184. Its totient is φ = 20463901504.

The previous prime is 21012009971. The next prime is 21012010027. The reversal of 21012010021 is 12001021012.

It is a cyclic number.

It is not a de Polignac number, because 21012010021 - 2⁹ = 21012009509 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21012010027) 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, 10648791 + ... + 10650763.

It is an arithmetic number, because the mean of its divisors is an integer number (1347799824).

Almost surely, 2^21012010021 is an apocalyptic number.

It is an amenable number.

21012010021 is a deficient number, since it is larger than the sum of its proper divisors (552787163).

21012010021 is a wasteful number, since it uses less digits than its factorization.

21012010021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3020.

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21012010021 its reverse (12001021012), we get a palindrome (33013031033).

The spelling of 21012010021 in words is "twenty-one billion, twelve million, ten thousand, twenty-one".