668881 has 4 divisors (see below), whose sum is σ = 671332. Its totient is φ = 666432.

The previous prime is 668879. The next prime is 668903. The reversal of 668881 is 188866.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 188866 = 2 ⋅94433.

It can be written as a sum of positive squares in 2 ways, for example, as 14400 + 654481 = 120^2 + 809^2 .

It is a cyclic number.

It is not a de Polignac number, because 668881 - 2¹ = 668879 is a prime.

It is a super-2 number, since 2×668881² = 894803584322, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 668881.

It is not an unprimeable number, because it can be changed into a prime (668821) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 756 + ... + 1381.

It is an arithmetic number, because the mean of its divisors is an integer number (167833).

2⁶⁶⁸⁸⁸¹ is an apocalyptic number.

It is an amenable number.

668881 is a deficient number, since it is larger than the sum of its proper divisors (2451).

668881 is a wasteful number, since it uses less digits than its factorization.

668881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2450.

The product of its digits is 18432, while the sum is 37.

The square root of 668881 is about 817.8514535049. The cubic root of 668881 is about 87.4546595028.

The spelling of 668881 in words is "six hundred sixty-eight thousand, eight hundred eighty-one".