666878720 has 144 divisors (see below), whose sum is σ = 1781468640. Its totient is φ = 237699072.

The previous prime is 666878717. The next prime is 666878731. The reversal of 666878720 is 27878666.

It is a happy number.

666878720 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Smith number, since the sum of its digits (50) coincides with the sum of the digits of its prime factors.

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, 412634 + ... + 414246.

It is an arithmetic number, because the mean of its divisors is an integer number (12371310).

Almost surely, 2^666878720 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 666878720, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (890734320).

666878720 is an abundant number, since it is smaller than the sum of its proper divisors (1114589920).

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

666878720 is a wasteful number, since it uses less digits than its factorization.

666878720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1670 (or 1656 counting only the distinct ones).

The product of its (nonzero) digits is 1354752, while the sum is 50.

The square root of 666878720 is about 25823.9950433700. The cubic root of 666878720 is about 873.6730777423.

It can be divided in two parts, 66 and 6878720, that added together give a palindrome (6878786).

The spelling of 666878720 in words is "six hundred sixty-six million, eight hundred seventy-eight thousand, seven hundred twenty".