817809681401856 has 5760 divisors, whose sum is σ = 3337344814003200. Its totient is φ = 196759624089600.

The previous prime is 817809681401819. The next prime is 817809681401857. The reversal of 817809681401856 is 658104186908718.

817809681401856 is a `hidden beast` number, since 8 + 1 + 7 + 8 + 0 + 96 + 81 + 401 + 8 + 56 = 666.

It is a Harshad number since it is a multiple of its sum of digits (72).

It is not an unprimeable number, because it can be changed into a prime (817809681401857) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 479 ways as a sum of consecutive naturals, for example, 2612810483556 + ... + 2612810483868.

It is an arithmetic number, because the mean of its divisors is an integer number (579400141320).

Almost surely, 2^{817809681401856} 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 817809681401856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1668672407001600).

817809681401856 is an abundant number, since it is smaller than the sum of its proper divisors (2519535132601344).

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

817809681401856 is a wasteful number, since it uses less digits than its factorization.

817809681401856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 449 (or 409 counting only the distinct ones).

The product of its (nonzero) digits is 185794560, while the sum is 72.

The spelling of 817809681401856 in words is "eight hundred seventeen trillion, eight hundred nine billion, six hundred eighty-one million, four hundred one thousand, eight hundred fifty-six".