638815 has 4 divisors (see below), whose sum is σ = 766584. Its totient is φ = 511048.

The previous prime is 638801. The next prime is 638819. The reversal of 638815 is 518836.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 638815 - 2⁹ = 638303 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638819) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63877 + ... + 63886.

It is an arithmetic number, because the mean of its divisors is an integer number (191646).

2⁶³⁸⁸¹⁵ is an apocalyptic number.

638815 is a deficient number, since it is larger than the sum of its proper divisors (127769).

638815 is a wasteful number, since it uses less digits than its factorization.

638815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127768.

The product of its digits is 5760, while the sum is 31.

The square root of 638815 is about 799.2590318539. The cubic root of 638815 is about 86.1241671343.

The spelling of 638815 in words is "six hundred thirty-eight thousand, eight hundred fifteen".