668645 has 8 divisors (see below), whose sum is σ = 808056. Its totient is φ = 531136.

The previous prime is 668623. The next prime is 668671. The reversal of 668645 is 546866.

It can be written as a sum of positive squares in 4 ways, for example, as 57121 + 611524 = 239^2 + 782^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 668645 - 2⁶ = 668581 is a prime.

It is a super-2 number, since 2×668645² = 894172272050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 479 + ... + 1251.

It is an arithmetic number, because the mean of its divisors is an integer number (101007).

2⁶⁶⁸⁶⁴⁵ is an apocalyptic number.

It is an amenable number.

668645 is a deficient number, since it is larger than the sum of its proper divisors (139411).

668645 is a wasteful number, since it uses less digits than its factorization.

668645 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 951.

The product of its digits is 34560, while the sum is 35.

The square root of 668645 is about 817.7071602964. The cubic root of 668645 is about 87.4443728064. Note that the first 3 decimals are identical.

The spelling of 668645 in words is "six hundred sixty-eight thousand, six hundred forty-five".