210002100021 has 48 divisors (see below), whose sum is σ = 367524871168. Its totient is φ = 112991500800.

The previous prime is 210002100017. The next prime is 210002100029. The reversal of 210002100021 is 120001200012.

It is not a de Polignac number, because 210002100021 - 2² = 210002100017 is a prime.

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

210002100021 is a modest number, since divided by 2100021 gives 21 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 210002099976 and 210002100012.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (210002100029) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1380820 + ... + 1525341.

Almost surely, 2^210002100021 is an apocalyptic number.

210002100021 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

210002100021 is a deficient number, since it is larger than the sum of its proper divisors (157522771147).

210002100021 is a wasteful number, since it uses less digits than its factorization.

210002100021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2906242 (or 2906239 counting only the distinct ones).

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

Adding to 210002100021 its reverse (120001200012), we get a palindrome (330003300033).

Subtracting from 210002100021 its reverse (120001200012), we obtain a palindrome (90000900009).

The spelling of 210002100021 in words is "two hundred ten billion, two million, one hundred thousand, twenty-one".