668399 has 4 divisors (see below), whose sum is σ = 676536. Its totient is φ = 660264.

The previous prime is 668347. The next prime is 668407. The reversal of 668399 is 993866.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-668399 is a prime.

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 3 ways as a sum of consecutive naturals, for example, 3944 + ... + 4109.

It is an arithmetic number, because the mean of its divisors is an integer number (169134).

2⁶⁶⁸³⁹⁹ is an apocalyptic number.

668399 is a deficient number, since it is larger than the sum of its proper divisors (8137).

668399 is an equidigital number, since it uses as much as digits as its factorization.

668399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8136.

The product of its digits is 69984, while the sum is 41.

The square root of 668399 is about 817.5567258607. The cubic root of 668399 is about 87.4336476561.

The spelling of 668399 in words is "six hundred sixty-eight thousand, three hundred ninety-nine".