21010010021 has 32 divisors (see below), whose sum is σ = 28382527488. Its totient is φ = 15019266240.

The previous prime is 21010010017. The next prime is 21010010027. The reversal of 21010010021 is 12001001012.

It is not a de Polignac number, because 21010010021 - 2² = 21010010017 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21010009990 and 21010010008.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21010010027) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 98780 + ... + 227546.

It is an arithmetic number, because the mean of its divisors is an integer number (886953984).

Almost surely, 2^21010010021 is an apocalyptic number.

It is an amenable number.

21010010021 is a deficient number, since it is larger than the sum of its proper divisors (7372517467).

21010010021 is a wasteful number, since it uses less digits than its factorization.

21010010021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128961.

The product of its (nonzero) digits is 4, while the sum is 8.

Adding to 21010010021 its reverse (12001001012), we get a palindrome (33011011033).

Subtracting from 21010010021 its reverse (12001001012), we obtain a palindrome (9009009009).

The spelling of 21010010021 in words is "twenty-one billion, ten million, ten thousand, twenty-one".