21212138856 has 64 divisors (see below), whose sum is σ = 54881323200. Its totient is φ = 6824115200.

The previous prime is 21212138819. The next prime is 21212138863. The reversal of 21212138856 is 65883121212.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2341696 + ... + 2350736.

It is an arithmetic number, because the mean of its divisors is an integer number (857520675).

Almost surely, 2^21212138856 is an apocalyptic number.

It is an amenable number.

21212138856 is an abundant number, since it is smaller than the sum of its proper divisors (33669184344).

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

21212138856 is a wasteful number, since it uses less digits than its factorization.

21212138856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12450 (or 12446 counting only the distinct ones).

The product of its digits is 46080, while the sum is 39.

The spelling of 21212138856 in words is "twenty-one billion, two hundred twelve million, one hundred thirty-eight thousand, eight hundred fifty-six".