638728 has 8 divisors (see below), whose sum is σ = 1197630. Its totient is φ = 319360.

The previous prime is 638719. The next prime is 638767. The reversal of 638728 is 827836.

It is a happy number.

638728 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 492804 + 145924 = 702^2 + 382^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is a junction number, because it is equal to n+sod(n) for n = 638693 and 638702.

It is an unprimeable number.

638728 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 as a sum of consecutive naturals, namely, 39913 + ... + 39928.

2⁶³⁸⁷²⁸ is an apocalyptic number.

It is an amenable number.

638728 is a deficient number, since it is larger than the sum of its proper divisors (558902).

638728 is a wasteful number, since it uses less digits than its factorization.

638728 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79847 (or 79843 counting only the distinct ones).

The product of its digits is 16128, while the sum is 34.

The square root of 638728 is about 799.2046045913. The cubic root of 638728 is about 86.1202572164.

It can be divided in two parts, 638 and 728, that multiplied together give a palindrome (464464).

The spelling of 638728 in words is "six hundred thirty-eight thousand, seven hundred twenty-eight".