21121211100 has 72 divisors (see below), whose sum is σ = 66666233088. Its totient is φ = 5120292800.

The previous prime is 21121211081. The next prime is 21121211113. The reversal of 21121211100 is 111212112.

It is a super-2 number, since 2×21121211100² (a number of 21 digits) contains 22 as substring.

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 pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3196884 + ... + 3203483.

It is an arithmetic number, because the mean of its divisors is an integer number (925919904).

Almost surely, 2^21121211100 is an apocalyptic number.

21121211100 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21121211100 is an abundant number, since it is smaller than the sum of its proper divisors (45545021988).

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

21121211100 is a wasteful number, since it uses less digits than its factorization.

21121211100 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6400395 (or 6400388 counting only the distinct ones).

The product of its (nonzero) digits is 8, while the sum is 12.

Adding to 21121211100 its reverse (111212112), we get a palindrome (21232423212).

It can be divided in two parts, 21121 and 211100, that added together give a triangular number (232221 = T₆₈₁).

The spelling of 21121211100 in words is "twenty-one billion, one hundred twenty-one million, two hundred eleven thousand, one hundred".