666400800 has 432 divisors, whose sum is σ = 2470341888. Its totient is φ = 155750400.

The previous prime is 666400793. The next prime is 666400837. The reversal of 666400800 is 8004666.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (30).

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 71 ways as a sum of consecutive naturals, for example, 12573574 + ... + 12573626.

It is an arithmetic number, because the mean of its divisors is an integer number (5718384).

Almost surely, 2^666400800 is an apocalyptic number.

666400800 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 666400800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1235170944).

666400800 is an abundant number, since it is smaller than the sum of its proper divisors (1803941088).

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

666400800 is a wasteful number, since it uses less digits than its factorization.

666400800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 133 (or 107 counting only the distinct ones).

The product of its (nonzero) digits is 6912, while the sum is 30.

The square root of 666400800 is about 25814.7399754481. The cubic root of 666400800 is about 873.4643213325.

The spelling of 666400800 in words is "six hundred sixty-six million, four hundred thousand, eight hundred".