21201222102100 has 72 divisors (see below), whose sum is σ = 47152670270328. Its totient is φ = 8269451059200.

The previous prime is 21201222102091. The next prime is 21201222102197. The reversal of 21201222102100 is 120122210212.

It is a happy number.

It can be written as a sum of positive squares in 12 ways, for example, as 12306428834704 + 8894793267396 = 3508052^2 + 2982414^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6778852 + ... + 9399748.

It is an arithmetic number, because the mean of its divisors is an integer number (654898198199).

Almost surely, 2^{21201222102100} is an apocalyptic number.

21201222102100 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 21201222102100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23576335135164).

21201222102100 is an abundant number, since it is smaller than the sum of its proper divisors (25951448168228).

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

21201222102100 is a wasteful number, since it uses less digits than its factorization.

21201222102100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2622925 (or 2622918 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21201222102100 its reverse (120122210212), we get a palindrome (21321344312312).

The spelling of 21201222102100 in words is "twenty-one trillion, two hundred one billion, two hundred twenty-two million, one hundred two thousand, one hundred".