21387856284 has 72 divisors (see below), whose sum is σ = 55372000320. Its totient is φ = 6957637632.

The previous prime is 21387856229. The next prime is 21387856297. The reversal of 21387856284 is 48265878312.

21387856284 is a `hidden beast` number, since 2 + 1 + 3 + 8 + 7 + 8 + 5 + 628 + 4 = 666.

It is a self number, because there is not a number n which added to its sum of digits gives 21387856284.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 579372 + ... + 615180.

It is an arithmetic number, because the mean of its divisors is an integer number (769055560).

Almost surely, 2^21387856284 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21387856284, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27686000160).

21387856284 is an abundant number, since it is smaller than the sum of its proper divisors (33984144036).

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

21387856284 is a wasteful number, since it uses less digits than its factorization.

21387856284 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36219 (or 36214 counting only the distinct ones).

The product of its digits is 5160960, while the sum is 54.

The spelling of 21387856284 in words is "twenty-one billion, three hundred eighty-seven million, eight hundred fifty-six thousand, two hundred eighty-four".