664649 has 4 divisors (see below), whose sum is σ = 703764. Its totient is φ = 625536.

The previous prime is 664633. The next prime is 664661. The reversal of 664649 is 946466.

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 399424 + 265225 = 632^2 + 515^2 .

It is a cyclic number.

It is not a de Polignac number, because 664649 - 2⁴ = 664633 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (664619) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19532 + ... + 19565.

It is an arithmetic number, because the mean of its divisors is an integer number (175941).

2⁶⁶⁴⁶⁴⁹ is an apocalyptic number.

It is an amenable number.

664649 is a deficient number, since it is larger than the sum of its proper divisors (39115).

664649 is a wasteful number, since it uses less digits than its factorization.

664649 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39114.

The product of its digits is 31104, while the sum is 35.

The square root of 664649 is about 815.2600812011. The cubic root of 664649 is about 87.2698277064.

The spelling of 664649 in words is "six hundred sixty-four thousand, six hundred forty-nine".