638686 has 4 divisors (see below), whose sum is σ = 958032. Its totient is φ = 319342.

The previous prime is 638669. The next prime is 638689. The reversal of 638686 is 686836.

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

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 as a sum of consecutive naturals, namely, 159670 + ... + 159673.

It is an arithmetic number, because the mean of its divisors is an integer number (239508).

2⁶³⁸⁶⁸⁶ is an apocalyptic number.

638686 is a deficient number, since it is larger than the sum of its proper divisors (319346).

638686 is a wasteful number, since it uses less digits than its factorization.

638686 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319345.

The product of its digits is 41472, while the sum is 37.

The square root of 638686 is about 799.1783280345. The cubic root of 638686 is about 86.1183695427.

The spelling of 638686 in words is "six hundred thirty-eight thousand, six hundred eighty-six".