668491 has 4 divisors (see below), whose sum is σ = 707832. Its totient is φ = 629152.

The previous prime is 668471. The next prime is 668509. The reversal of 668491 is 194866.

668491 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 668491 - 2¹³ = 660299 is a prime.

It is a Duffinian number.

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (668471) 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, 19645 + ... + 19678.

It is an arithmetic number, because the mean of its divisors is an integer number (176958).

2⁶⁶⁸⁴⁹¹ is an apocalyptic number.

668491 is a deficient number, since it is larger than the sum of its proper divisors (39341).

668491 is a wasteful number, since it uses less digits than its factorization.

668491 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39340.

The product of its digits is 10368, while the sum is 34.

The square root of 668491 is about 817.6129891336. The cubic root of 668491 is about 87.4376589959.

The spelling of 668491 in words is "six hundred sixty-eight thousand, four hundred ninety-one".