664399 has 4 divisors (see below), whose sum is σ = 675720. Its totient is φ = 653080.

The previous prime is 664381. The next prime is 664403. The reversal of 664399 is 993466.

664399 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: 993466 = 2 ⋅496733.

It is a cyclic number.

It is not a de Polignac number, because 664399 - 2⁷ = 664271 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 (664319) 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, 5572 + ... + 5689.

It is an arithmetic number, because the mean of its divisors is an integer number (168930).

2⁶⁶⁴³⁹⁹ is an apocalyptic number.

664399 is a deficient number, since it is larger than the sum of its proper divisors (11321).

664399 is a wasteful number, since it uses less digits than its factorization.

664399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11320.

The product of its digits is 34992, while the sum is 37.

The square root of 664399 is about 815.1067414762. The cubic root of 664399 is about 87.2588844903.

It can be divided in two parts, 66 and 4399, that added together give a triangular number (4465 = T₉₄).

The spelling of 664399 in words is "six hundred sixty-four thousand, three hundred ninety-nine".