21200021100 has 108 divisors (see below), whose sum is σ = 66973880064. Its totient is φ = 5608794240.

The previous prime is 21200021047. The next prime is 21200021107. The reversal of 21200021100 is 112000212.

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

It is not an unprimeable number, because it can be changed into a prime (21200021107) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 21562 + ... + 207038.

Almost surely, 2^21200021100 is an apocalyptic number.

21200021100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21200021100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33486940032).

21200021100 is an abundant number, since it is smaller than the sum of its proper divisors (45773858964).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21200021100 is a wasteful number, since it uses less digits than its factorization.

21200021100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 185624 (or 185614 counting only the distinct ones).

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

Adding to 21200021100 its reverse (112000212), we get a palindrome (21312021312).

The spelling of 21200021100 in words is "twenty-one billion, two hundred million, twenty-one thousand, one hundred".