21201122100 has 144 divisors (see below), whose sum is σ = 63626927616. Its totient is φ = 5446080000.

The previous prime is 21201122077. The next prime is 21201122113. The reversal of 21201122100 is 122110212.

It is a Harshad number since it is a multiple of its sum of digits (12).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1111645 + ... + 1130555.

It is an arithmetic number, because the mean of its divisors is an integer number (441853664).

Almost surely, 2^21201122100 is an apocalyptic number.

21201122100 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 21201122100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31813463808).

21201122100 is an abundant number, since it is smaller than the sum of its proper divisors (42425805516).

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

21201122100 is a wasteful number, since it uses less digits than its factorization.

21201122100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19066 (or 19059 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21201122100 its reverse (122110212), we get a palindrome (21323232312).

It can be divided in two parts, 2120112 and 2100, that added together give a palindrome (2122212).

The spelling of 21201122100 in words is "twenty-one billion, two hundred one million, one hundred twenty-two thousand, one hundred".