668591 has 16 divisors (see below), whose sum is σ = 879360. Its totient is φ = 492480.

The previous prime is 668581. The next prime is 668599. The reversal of 668591 is 195866.

It is not a de Polignac number, because 668591 - 2⁶ = 668527 is a prime.

It is a Smith number, since the sum of its digits (35) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (668599) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1235 + ... + 1691.

It is an arithmetic number, because the mean of its divisors is an integer number (54960).

2⁶⁶⁸⁵⁹¹ is an apocalyptic number.

668591 is a deficient number, since it is larger than the sum of its proper divisors (210769).

668591 is a wasteful number, since it uses less digits than its factorization.

668591 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 494.

The product of its digits is 12960, while the sum is 35.

The square root of 668591 is about 817.6741404741. The cubic root of 668591 is about 87.4420187305.

It can be divided in two parts, 6685 and 91, that added together give a palindrome (6776).

The spelling of 668591 in words is "six hundred sixty-eight thousand, five hundred ninety-one".