666640800 has 288 divisors, whose sum is σ = 2756073600. Its totient is φ = 152340480.

The previous prime is 666640769. The next prime is 666640813. The reversal of 666640800 is 8046666.

It is a tau number, because it is divible by the number of its divisors (288).

It is a Harshad number since it is a multiple of its sum of digits (36).

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 47 ways as a sum of consecutive naturals, for example, 148996 + ... + 153404.

It is an arithmetic number, because the mean of its divisors is an integer number (9569700).

Almost surely, 2^666640800 is an apocalyptic number.

666640800 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 666640800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1378036800).

666640800 is an abundant number, since it is smaller than the sum of its proper divisors (2089432800).

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

666640800 is a wasteful number, since it uses less digits than its factorization.

666640800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4445 (or 4426 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

The square root of 666640800 is about 25819.3880640111. The cubic root of 666640800 is about 873.5691662828.

The spelling of 666640800 in words is "six hundred sixty-six million, six hundred forty thousand, eight hundred".