20815856856 has 192 divisors, whose sum is σ = 60463260000. Its totient is φ = 6446813184.

The previous prime is 20815856827. The next prime is 20815856879. The reversal of 20815856856 is 65865851802.

20815856856 is a `hidden beast` number, since 2 + 0 + 8 + 1 + 585 + 6 + 8 + 56 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 41714895 + ... + 41715393.

Almost surely, 2^20815856856 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 20815856856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (30231630000).

20815856856 is an abundant number, since it is smaller than the sum of its proper divisors (39647403144).

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

20815856856 is a wasteful number, since it uses less digits than its factorization.

20815856856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 898 (or 891 counting only the distinct ones).

The product of its (nonzero) digits is 4608000, while the sum is 54.

The spelling of 20815856856 in words is "twenty billion, eight hundred fifteen million, eight hundred fifty-six thousand, eight hundred fifty-six".