638668 has 6 divisors (see below), whose sum is σ = 1117676. Its totient is φ = 319332.

The previous prime is 638663. The next prime is 638669. The reversal of 638668 is 866836.

It is an Ulam number.

It is not an unprimeable number, because it can be changed into a prime (638663) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 79830 + ... + 79837.

2⁶³⁸⁶⁶⁸ is an apocalyptic number.

It is an amenable number.

638668 is a deficient number, since it is larger than the sum of its proper divisors (479008).

638668 is a wasteful number, since it uses less digits than its factorization.

638668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 159671 (or 159669 counting only the distinct ones).

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

The square root of 638668 is about 799.1670663885. The cubic root of 638668 is about 86.1175605144.

The spelling of 638668 in words is "six hundred thirty-eight thousand, six hundred sixty-eight".