666561208320 has 896 divisors, whose sum is σ = 2744417249280. Its totient is φ = 152213520384.

The previous prime is 666561208319. The next prime is 666561208349. The reversal of 666561208320 is 23802165666.

It is a tau number, because it is divible by the number of its divisors (896).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 627056109 + ... + 627057171.

It is an arithmetic number, because the mean of its divisors is an integer number (3062965680).

Almost surely, 2^666561208320 is an apocalyptic number.

666561208320 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 666561208320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1372208624640).

666561208320 is an abundant number, since it is smaller than the sum of its proper divisors (2077856040960).

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

666561208320 is an frugal number, since it uses more digits than its factorization.

666561208320 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1122 (or 1080 counting only the distinct ones).

The product of its (nonzero) digits is 622080, while the sum is 45.

The spelling of 666561208320 in words is "six hundred sixty-six billion, five hundred sixty-one million, two hundred eight thousand, three hundred twenty".