638656 has 28 divisors (see below), whose sum is σ = 1344168. Its totient is φ = 300032.

The previous prime is 638633. The next prime is 638663. The reversal of 638656 is 656836.

638656 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (34).

It is an unprimeable number.

638656 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 795 + ... + 1381.

It is an arithmetic number, because the mean of its divisors is an integer number (48006).

2⁶³⁸⁶⁵⁶ 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 638656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (672084).

638656 is an abundant number, since it is smaller than the sum of its proper divisors (705512).

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

638656 is a wasteful number, since it uses less digits than its factorization.

638656 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 616 (or 606 counting only the distinct ones).

The product of its digits is 25920, while the sum is 34.

The square root of 638656 is about 799.1595585363. The cubic root of 638656 is about 86.1170211537.

The spelling of 638656 in words is "six hundred thirty-eight thousand, six hundred fifty-six".