21002010021 has 16 divisors (see below), whose sum is σ = 31134741120. Its totient is φ = 13992046560.

The previous prime is 21002009957. The next prime is 21002010023. The reversal of 21002010021 is 12001020012.

It is not a de Polignac number, because 21002010021 - 2⁶ = 21002009957 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (9).

It is a junction number, because it is equal to n+sod(n) for n = 21002009985 and 21002010012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002010023) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 216600 + ... + 298193.

It is an arithmetic number, because the mean of its divisors is an integer number (1945921320).

Almost surely, 2^21002010021 is an apocalyptic number.

It is an amenable number.

21002010021 is a deficient number, since it is larger than the sum of its proper divisors (10132731099).

21002010021 is a wasteful number, since it uses less digits than its factorization.

21002010021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 516313 (or 516307 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 9.

Adding to 21002010021 its reverse (12001020012), we get a palindrome (33003030033).

Subtracting from 21002010021 its reverse (12001020012), we obtain a palindrome (9000990009).

The spelling of 21002010021 in words is "twenty-one billion, two million, ten thousand, twenty-one".