21100021212 has 12 divisors (see below), whose sum is σ = 49233382856. Its totient is φ = 7033340400.

The previous prime is 21100021157. The next prime is 21100021249. The reversal of 21100021212 is 21212000112.

It is a tau number, because it is divible by the number of its divisors (12).

It is a super-3 number, since 3×21100021212³ (a number of 32 digits) contains 333 as substring.

It is a Harshad number since it is a multiple of its sum of digits (12), and also a Moran number because the ratio is a prime number: 1758335101 = 21100021212 / (2 + 1 + 1 + 0 + 0 + 0 + 2 + 1 + 2 + 1 + 2).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 879167539 + ... + 879167562.

Almost surely, 2^21100021212 is an apocalyptic number.

It is an amenable number.

21100021212 is an abundant number, since it is smaller than the sum of its proper divisors (28133361644).

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

21100021212 is a wasteful number, since it uses less digits than its factorization.

21100021212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1758335108 (or 1758335106 counting only the distinct ones).

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

Adding to 21100021212 its reverse (21212000112), we get a palindrome (42312021324).

The spelling of 21100021212 in words is "twenty-one billion, one hundred million, twenty-one thousand, two hundred twelve".