668557680 has 80 divisors (see below), whose sum is σ = 2368610304. Its totient is φ = 152812800.

The previous prime is 668557649. The next prime is 668557697. The reversal of 668557680 is 86755866.

668557680 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a tau number, because it is divible by the number of its divisors (80).

It is a hoax number, since the sum of its digits (51) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 197296 + ... + 200655.

Almost surely, 2^668557680 is an apocalyptic number.

668557680 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

668557680 is an abundant number, since it is smaller than the sum of its proper divisors (1700052624).

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

668557680 is a wasteful number, since it uses less digits than its factorization.

668557680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 397974 (or 397968 counting only the distinct ones).

The product of its (nonzero) digits is 2419200, while the sum is 51.

The square root of 668557680 is about 25856.4823593620. The cubic root of 668557680 is about 874.4056611520.

The spelling of 668557680 in words is "six hundred sixty-eight million, five hundred fifty-seven thousand, six hundred eighty".