638685 has 40 divisors (see below), whose sum is σ = 1219680. Its totient is φ = 318816.

The previous prime is 638669. The next prime is 638689. The reversal of 638685 is 586836.

It is not a de Polignac number, because 638685 - 2⁴ = 638669 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638689) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 7654 + ... + 7736.

It is an arithmetic number, because the mean of its divisors is an integer number (30492).

2⁶³⁸⁶⁸⁵ is an apocalyptic number.

It is an amenable number.

638685 is a deficient number, since it is larger than the sum of its proper divisors (580995).

638685 is a wasteful number, since it uses less digits than its factorization.

638685 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119 (or 110 counting only the distinct ones).

The product of its digits is 34560, while the sum is 36.

The square root of 638685 is about 799.1777023917. The cubic root of 638685 is about 86.1183245971.

The spelling of 638685 in words is "six hundred thirty-eight thousand, six hundred eighty-five".