664813 has 4 divisors (see below), whose sum is σ = 668668. Its totient is φ = 660960.

The previous prime is 664799. The next prime is 664843. The reversal of 664813 is 318466.

664813 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, and also an emirpimes, since its reverse is a distinct semiprime: 318466 = 2 ⋅159233.

It can be written as a sum of positive squares in 2 ways, for example, as 21609 + 643204 = 147^2 + 802^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-664813 is a prime.

It is a Duffinian number.

664813 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664843) 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, 1656 + ... + 2017.

It is an arithmetic number, because the mean of its divisors is an integer number (167167).

2⁶⁶⁴⁸¹³ is an apocalyptic number.

It is an amenable number.

664813 is a deficient number, since it is larger than the sum of its proper divisors (3855).

664813 is a wasteful number, since it uses less digits than its factorization.

664813 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3854.

The product of its digits is 3456, while the sum is 28.

The square root of 664813 is about 815.3606563969. The cubic root of 664813 is about 87.2770049658.

The spelling of 664813 in words is "six hundred sixty-four thousand, eight hundred thirteen".