21000111220 has 96 divisors (see below), whose sum is σ = 51121881216. Its totient is φ = 7161446400.

The previous prime is 21000111179. The next prime is 21000111227. The reversal of 21000111220 is 2211100012.

It is a Harshad number since it is a multiple of its sum of digits (10).

It is a junction number, because it is equal to n+sod(n) for n = 21000111197 and 21000111206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000111227) 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, 1048500 + ... + 1068340.

It is an arithmetic number, because the mean of its divisors is an integer number (532519596).

Almost surely, 2^21000111220 is an apocalyptic number.

21000111220 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 21000111220, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25560940608).

21000111220 is an abundant number, since it is smaller than the sum of its proper divisors (30121769996).

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

21000111220 is a wasteful number, since it uses less digits than its factorization.

21000111220 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20161 (or 20159 counting only the distinct ones).

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

Adding to 21000111220 its reverse (2211100012), we get a palindrome (23211211232).

The spelling of 21000111220 in words is "twenty-one billion, one hundred eleven thousand, two hundred twenty".