21012111221100 has 144 divisors (see below), whose sum is σ = 61950740211360. Its totient is φ = 5496743116800.

The previous prime is 21012111221009. The next prime is 21012111221107. The reversal of 21012111221100 is 112211121012.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a self number, because there is not a number n which added to its sum of digits gives 21012111221100.

It is not an unprimeable number, because it can be changed into a prime (21012111221107) 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, 118986870 + ... + 119163330.

It is an arithmetic number, because the mean of its divisors is an integer number (430213473690).

Almost surely, 2^{21012111221100} is an apocalyptic number.

21012111221100 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 21012111221100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30975370105680).

21012111221100 is an abundant number, since it is smaller than the sum of its proper divisors (40938628990260).

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

21012111221100 is a wasteful number, since it uses less digits than its factorization.

21012111221100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 184020 (or 184013 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 15.

Adding to 21012111221100 its reverse (112211121012), we get a palindrome (21124322342112).

The spelling of 21012111221100 in words is "twenty-one trillion, twelve billion, one hundred eleven million, two hundred twenty-one thousand, one hundred".