639688 has 16 divisors (see below), whose sum is σ = 1370880. Its totient is φ = 274128.

The previous prime is 639679. The next prime is 639689. The reversal of 639688 is 886936.

It is a self number, because there is not a number n which added to its sum of digits gives 639688.

It is not an unprimeable number, because it can be changed into a prime (639689) by changing a digit.

639688 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5656 + ... + 5767.

It is an arithmetic number, because the mean of its divisors is an integer number (85680).

2⁶³⁹⁶⁸⁸ is an apocalyptic number.

It is an amenable number.

639688 is an abundant number, since it is smaller than the sum of its proper divisors (731192).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639688 is a wasteful number, since it uses less digits than its factorization.

639688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11436 (or 11432 counting only the distinct ones).

The product of its digits is 62208, while the sum is 40.

The square root of 639688 is about 799.8049762286. The cubic root of 639688 is about 86.1633814996.

The spelling of 639688 in words is "six hundred thirty-nine thousand, six hundred eighty-eight".