664889 has 4 divisors (see below), whose sum is σ = 666660. Its totient is φ = 663120.

The previous prime is 664879. The next prime is 664891. The reversal of 664889 is 988466.

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

It can be written as a sum of positive squares in 2 ways, for example, as 511225 + 153664 = 715^2 + 392^2 .

It is a cyclic number.

It is not a de Polignac number, because 664889 - 2⁸ = 664633 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 (664849) 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, 74 + ... + 1155.

It is an arithmetic number, because the mean of its divisors is an integer number (166665).

2⁶⁶⁴⁸⁸⁹ is an apocalyptic number.

It is an amenable number.

664889 is a deficient number, since it is larger than the sum of its proper divisors (1771).

664889 is a wasteful number, since it uses less digits than its factorization.

664889 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1770.

The product of its digits is 82944, while the sum is 41.

The square root of 664889 is about 815.4072602081. The cubic root of 664889 is about 87.2803306126.

The spelling of 664889 in words is "six hundred sixty-four thousand, eight hundred eighty-nine".