638664 has 64 divisors (see below), whose sum is σ = 1814400. Its totient is φ = 185856.

The previous prime is 638663. The next prime is 638669. The reversal of 638664 is 466836.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 7132 + ... + 7220.

It is an arithmetic number, because the mean of its divisors is an integer number (28350).

2⁶³⁸⁶⁶⁴ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 638664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (907200).

638664 is an abundant number, since it is smaller than the sum of its proper divisors (1175736).

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

638664 is a wasteful number, since it uses less digits than its factorization.

638664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134 (or 130 counting only the distinct ones).

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

The square root of 638664 is about 799.1645637790. The cubic root of 638664 is about 86.1173807282.

The spelling of 638664 in words is "six hundred thirty-eight thousand, six hundred sixty-four".