668659 has 4 divisors (see below), whose sum is σ = 672040. Its totient is φ = 665280.

The previous prime is 668623. The next prime is 668671. The reversal of 668659 is 956866.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 956866 = 2 ⋅478433.

It is a cyclic number.

It is not a de Polignac number, because 668659 - 2⁷ = 668531 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (668609) 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, 1374 + ... + 1795.

It is an arithmetic number, because the mean of its divisors is an integer number (168010).

2⁶⁶⁸⁶⁵⁹ is an apocalyptic number.

668659 is a deficient number, since it is larger than the sum of its proper divisors (3381).

668659 is a wasteful number, since it uses less digits than its factorization.

668659 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3380.

The product of its digits is 77760, while the sum is 40.

The square root of 668659 is about 817.7157207734. The cubic root of 668659 is about 87.4449831016. Note that the first 3 decimals are identical.

The spelling of 668659 in words is "six hundred sixty-eight thousand, six hundred fifty-nine".