640811666880 has 1344 divisors, whose sum is σ = 2947118515200. Its totient is φ = 129522032640.

The previous prime is 640811666867. The next prime is 640811666909. The reversal of 640811666880 is 88666118046.

It is a tau number, because it is divible by the number of its divisors (1344).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 172305661 + ... + 172309379.

Almost surely, 2^640811666880 is an apocalyptic number.

640811666880 is a gapful number since it is divisible by the number (60) 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 640811666880, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1473559257600).

640811666880 is an abundant number, since it is smaller than the sum of its proper divisors (2306306848320).

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

640811666880 is a wasteful number, since it uses less digits than its factorization.

640811666880 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3807 (or 3784 counting only the distinct ones).

The product of its (nonzero) digits is 2654208, while the sum is 54.

It can be divided in two parts, 64081166 and 6880, that added together give a palindrome (64088046).

The spelling of 640811666880 in words is "six hundred forty billion, eight hundred eleven million, six hundred sixty-six thousand, eight hundred eighty".