21201222100 has 144 divisors (see below), whose sum is σ = 47839993600. Its totient is φ = 8151736320.

The previous prime is 21201222089. The next prime is 21201222101. The reversal of 21201222100 is 122210212.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21201222101) 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, 55939711 + ... + 55940089.

Almost surely, 2^21201222100 is an apocalyptic number.

21201222100 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 21201222100, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23919996800).

21201222100 is an abundant number, since it is smaller than the sum of its proper divisors (26638771500).

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

21201222100 is a wasteful number, since it uses less digits than its factorization.

21201222100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 642 (or 635 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 21201222100 its reverse (122210212), we get a palindrome (21323432312).

The spelling of 21201222100 in words is "twenty-one billion, two hundred one million, two hundred twenty-two thousand, one hundred".