1665680785920 has 640 divisors, whose sum is σ = 6196826592000. Its totient is φ = 428823134208.

The previous prime is 1665680785831. The next prime is 1665680785939. The reversal of 1665680785920 is 295870865661.

1665680785920 is a `hidden beast` number, since 1 + 66 + 568 + 0 + 7 + 8 + 5 + 9 + 2 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (640).

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 162357751 + ... + 162368009.

It is an arithmetic number, because the mean of its divisors is an integer number (9682541550).

Almost surely, 2^{1665680785920} is an apocalyptic number.

1665680785920 is a gapful number since it is divisible by the number (10) 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 1665680785920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3098413296000).

1665680785920 is an abundant number, since it is smaller than the sum of its proper divisors (4531145806080).

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

1665680785920 is an frugal number, since it uses more digits than its factorization.

1665680785920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10332 (or 10298 counting only the distinct ones).

The product of its (nonzero) digits is 43545600, while the sum is 63.

The spelling of 1665680785920 in words is "one trillion, six hundred sixty-five billion, six hundred eighty million, seven hundred eighty-five thousand, nine hundred twenty".