638809 has 8 divisors (see below), whose sum is σ = 690120. Its totient is φ = 589056.

The previous prime is 638801. The next prime is 638819. The reversal of 638809 is 908836.

It can be written as a sum of positive squares in 4 ways, for example, as 120409 + 518400 = 347^2 + 720^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 638809 - 2³ = 638801 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (638801) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 547 + ... + 1255.

It is an arithmetic number, because the mean of its divisors is an integer number (86265).

2⁶³⁸⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

638809 is a deficient number, since it is larger than the sum of its proper divisors (51311).

638809 is a wasteful number, since it uses less digits than its factorization.

638809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 779.

The product of its (nonzero) digits is 10368, while the sum is 34.

The square root of 638809 is about 799.2552783686. The cubic root of 638809 is about 86.1238974962.

The spelling of 638809 in words is "six hundred thirty-eight thousand, eight hundred nine".