639867 has 4 divisors (see below), whose sum is σ = 853160. Its totient is φ = 426576.

The previous prime is 639857. The next prime is 639907. The reversal of 639867 is 768936.

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

It is not a de Polignac number, because 639867 - 2⁴ = 639851 is a prime.

It is a D-number.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639867.

It is not an unprimeable number, because it can be changed into a prime (639857) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 106642 + ... + 106647.

It is an arithmetic number, because the mean of its divisors is an integer number (213290).

2⁶³⁹⁸⁶⁷ is an apocalyptic number.

639867 is a deficient number, since it is larger than the sum of its proper divisors (213293).

639867 is a wasteful number, since it uses less digits than its factorization.

639867 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213292.

The product of its digits is 54432, while the sum is 39.

The square root of 639867 is about 799.9168706809. The cubic root of 639867 is about 86.1714176083.

The spelling of 639867 in words is "six hundred thirty-nine thousand, eight hundred sixty-seven".