66856535418816 has 336 divisors, whose sum is σ = 225156962179968. Its totient is φ = 18699247872000.

The previous prime is 66856535418787. The next prime is 66856535418851. The reversal of 66856535418816 is 61881453565866.

66856535418816 is a `hidden beast` number, since 6 + 6 + 8 + 5 + 6 + 535 + 4 + 1 + 8 + 81 + 6 = 666.

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

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, 954362991 + ... + 954433041.

It is an arithmetic number, because the mean of its divisors is an integer number (670110006488).

Almost surely, 2^{66856535418816} is an apocalyptic number.

66856535418816 is a gapful number since it is divisible by the number (66) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66856535418816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (112578481089984).

66856535418816 is an abundant number, since it is smaller than the sum of its proper divisors (158300426761152).

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

66856535418816 is a wasteful number, since it uses less digits than its factorization.

66856535418816 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 81680 (or 81667 counting only the distinct ones).

The product of its digits is 995328000, while the sum is 72.

The spelling of 66856535418816 in words is "sixty-six trillion, eight hundred fifty-six billion, five hundred thirty-five million, four hundred eighteen thousand, eight hundred sixteen".