21251815212 has 24 divisors (see below), whose sum is σ = 50078537712. Its totient is φ = 7013800000.

The previous prime is 21251815199. The next prime is 21251815219.

21251815212 is nontrivially palindromic in base 10.

It is a self number, because there is not a number n which added to its sum of digits gives 21251815212.

It is not an unprimeable number, because it can be changed into a prime (21251815219) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8766039 + ... + 8768462.

It is an arithmetic number, because the mean of its divisors is an integer number (2086605738).

Almost surely, 2^21251815212 is an apocalyptic number.

It is an amenable number.

21251815212 is an abundant number, since it is smaller than the sum of its proper divisors (28826722500).

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

21251815212 is a wasteful number, since it uses less digits than its factorization.

21251815212 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17534609 (or 17534607 counting only the distinct ones).

The product of its digits is 3200, while the sum is 30.

The spelling of 21251815212 in words is "twenty-one billion, two hundred fifty-one million, eight hundred fifteen thousand, two hundred twelve".