639685 has 8 divisors (see below), whose sum is σ = 792576. Its totient is φ = 495120.

The previous prime is 639679. The next prime is 639689. The reversal of 639685 is 586936.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 639685 - 2³ = 639677 is a prime.

It is a Duffinian number.

It is a congruent number.

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

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1909 + ... + 2218.

It is an arithmetic number, because the mean of its divisors is an integer number (99072).

2⁶³⁹⁶⁸⁵ is an apocalyptic number.

It is an amenable number.

639685 is a deficient number, since it is larger than the sum of its proper divisors (152891).

639685 is a wasteful number, since it uses less digits than its factorization.

639685 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4163.

The product of its digits is 38880, while the sum is 37.

The square root of 639685 is about 799.8031007692. The cubic root of 639685 is about 86.1632468034.

The spelling of 639685 in words is "six hundred thirty-nine thousand, six hundred eighty-five".