666881 has 4 divisors (see below), whose sum is σ = 702000. Its totient is φ = 631764.

The previous prime is 666871. The next prime is 666889. The reversal of 666881 is 188666.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 666881 - 2¹⁰ = 665857 is a prime.

It is a super-2 number, since 2×666881² = 889460536322, which contains 22 as substring.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 666881.

It is not an unprimeable number, because it can be changed into a prime (666889) 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 3 ways as a sum of consecutive naturals, for example, 17531 + ... + 17568.

It is an arithmetic number, because the mean of its divisors is an integer number (175500).

2⁶⁶⁶⁸⁸¹ is an apocalyptic number.

It is an amenable number.

666881 is a deficient number, since it is larger than the sum of its proper divisors (35119).

666881 is a wasteful number, since it uses less digits than its factorization.

666881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 35118.

The product of its digits is 13824, while the sum is 35.

The square root of 666881 is about 816.6278222054. The cubic root of 666881 is about 87.3674073412.

The spelling of 666881 in words is "six hundred sixty-six thousand, eight hundred eighty-one".