664638 has 16 divisors (see below), whose sum is σ = 1431696. Its totient is φ = 204480.

The previous prime is 664633. The next prime is 664661. The reversal of 664638 is 836466.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 664599 and 664608.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 664638.

It is not an unprimeable number, because it can be changed into a prime (664633) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4183 + ... + 4338.

It is an arithmetic number, because the mean of its divisors is an integer number (89481).

2⁶⁶⁴⁶³⁸ is an apocalyptic number.

664638 is an abundant number, since it is smaller than the sum of its proper divisors (767058).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

664638 is a wasteful number, since it uses less digits than its factorization.

664638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8539.

The product of its digits is 20736, while the sum is 33.

The square root of 664638 is about 815.2533348598. The cubic root of 664638 is about 87.2693462626.

The spelling of 664638 in words is "six hundred sixty-four thousand, six hundred thirty-eight".