638684 has 6 divisors (see below), whose sum is σ = 1117704. Its totient is φ = 319340.

The previous prime is 638669. The next prime is 638689. The reversal of 638684 is 486836.

It is a congruent number.

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

638684 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

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 as a sum of consecutive naturals, namely, 79832 + ... + 79839.

It is an arithmetic number, because the mean of its divisors is an integer number (186284).

2⁶³⁸⁶⁸⁴ is an apocalyptic number.

It is an amenable number.

638684 is a deficient number, since it is larger than the sum of its proper divisors (479020).

638684 is a wasteful number, since it uses less digits than its factorization.

638684 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 159675 (or 159673 counting only the distinct ones).

The product of its digits is 27648, while the sum is 35.

The square root of 638684 is about 799.1770767483. The cubic root of 638684 is about 86.1182796514.

The spelling of 638684 in words is "six hundred thirty-eight thousand, six hundred eighty-four".