666944 has 28 divisors (see below), whose sum is σ = 1403604. Its totient is φ = 313344.

The previous prime is 666937. The next prime is 666959. The reversal of 666944 is 449666.

It can be written as a sum of positive squares in 2 ways, for example, as 193600 + 473344 = 440^2 + 688^2 .

It is a plaindrome in base 9.

It is a congruent number.

It is an unprimeable number.

666944 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 3 ways as a sum of consecutive naturals, for example, 782 + ... + 1394.

2⁶⁶⁶⁹⁴⁴ is an apocalyptic number.

666944 is a gapful number since it is divisible by the number (64) 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 666944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (701802).

666944 is an abundant number, since it is smaller than the sum of its proper divisors (736660).

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

666944 is a wasteful number, since it uses less digits than its factorization.

666944 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 642 (or 632 counting only the distinct ones).

The product of its digits is 31104, while the sum is 35.

The square root of 666944 is about 816.6663945578. Note that the first 3 decimals coincide. The cubic root of 666944 is about 87.3701584434.

The spelling of 666944 in words is "six hundred sixty-six thousand, nine hundred forty-four".