638985 has 16 divisors (see below), whose sum is σ = 1048320. Its totient is φ = 332160.

The previous prime is 638977. The next prime is 638993. The reversal of 638985 is 589836.

It is an interprime number because it is at equal distance from previous prime (638977) and next prime (638993).

It is not a de Polignac number, because 638985 - 2³ = 638977 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 96 + ... + 1134.

It is an arithmetic number, because the mean of its divisors is an integer number (65520).

2⁶³⁸⁹⁸⁵ is an apocalyptic number.

It is an amenable number.

638985 is a deficient number, since it is larger than the sum of its proper divisors (409335).

638985 is a wasteful number, since it uses less digits than its factorization.

638985 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1088.

The product of its digits is 51840, while the sum is 39.

The square root of 638985 is about 799.3653732806. The cubic root of 638985 is about 86.1318061795.

It can be divided in two parts, 63898 and 5, that added together give a triangular number (63903 = T₃₅₇).

The spelling of 638985 in words is "six hundred thirty-eight thousand, nine hundred eighty-five".