21000212120 has 16 divisors (see below), whose sum is σ = 47250477360. Its totient is φ = 8400084832.

The previous prime is 21000212113. The next prime is 21000212143. The reversal of 21000212120 is 2121200012.

It is a happy number.

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 3 ways as a sum of consecutive naturals, for example, 262502612 + ... + 262502691.

It is an arithmetic number, because the mean of its divisors is an integer number (2953154835).

Almost surely, 2^21000212120 is an apocalyptic number.

21000212120 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21000212120 is an abundant number, since it is smaller than the sum of its proper divisors (26250265240).

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

21000212120 is a wasteful number, since it uses less digits than its factorization.

21000212120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 525005314 (or 525005310 counting only the distinct ones).

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21000212120 its reverse (2121200012), we get a palindrome (23121412132).

The spelling of 21000212120 in words is "twenty-one billion, two hundred twelve thousand, one hundred twenty".