666816 has 56 divisors (see below), whose sum is σ = 1853184. Its totient is φ = 211200.

The previous prime is 666811. The next prime is 666821. The reversal of 666816 is 618666.

It is an interprime number because it is at equal distance from previous prime (666811) and next prime (666821).

It is a nude number because it is divisible by every one of its digits.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 666816.

It is not an unprimeable number, because it can be changed into a prime (666811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4341 + ... + 4491.

2⁶⁶⁶⁸¹⁶ 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 666816, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (926592).

666816 is an abundant number, since it is smaller than the sum of its proper divisors (1186368).

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

666816 is a wasteful number, since it uses less digits than its factorization.

666816 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189 (or 179 counting only the distinct ones).

The product of its digits is 10368, while the sum is 33.

The square root of 666816 is about 816.5880234243. The cubic root of 666816 is about 87.3645687208.

The spelling of 666816 in words is "six hundred sixty-six thousand, eight hundred sixteen".