1665778716864 has 196 divisors, whose sum is σ = 4959517142160. Its totient is φ = 554868610560.

The previous prime is 1665778716863. The next prime is 1665778716907. The reversal of 1665778716864 is 4686178775661.

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

It is a junction number, because it is equal to n+sod(n) for n = 1665778716792 and 1665778716801.

It is not an unprimeable number, because it can be changed into a prime (1665778716863) by changing a digit.

It is a polite number, since it can be written in 27 ways as a sum of consecutive naturals, for example, 70485402 + ... + 70509030.

Almost surely, 2^{1665778716864} 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 1665778716864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2479758571080).

1665778716864 is an abundant number, since it is smaller than the sum of its proper divisors (3293738425296).

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

1665778716864 is an equidigital number, since it uses as much as digits as its factorization.

1665778716864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25170 (or 25145 counting only the distinct ones).

The product of its digits is 568995840, while the sum is 72.

The spelling of 1665778716864 in words is "one trillion, six hundred sixty-five billion, seven hundred seventy-eight million, seven hundred sixteen thousand, eight hundred sixty-four".