639895 has 4 divisors (see below), whose sum is σ = 767880. Its totient is φ = 511912.

The previous prime is 639857. The next prime is 639907. The reversal of 639895 is 598936.

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

It is a cyclic number.

It is not a de Polignac number, because 639895 - 2¹⁵ = 607127 is a prime.

It is a super-2 number, since 2×639895² = 818931222050, which contains 22 as substring.

It is a Smith number, since the sum of its digits (40) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 63985 + ... + 63994.

It is an arithmetic number, because the mean of its divisors is an integer number (191970).

2⁶³⁹⁸⁹⁵ is an apocalyptic number.

639895 is a deficient number, since it is larger than the sum of its proper divisors (127985).

639895 is a wasteful number, since it uses less digits than its factorization.

639895 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127984.

The product of its digits is 58320, while the sum is 40.

The square root of 639895 is about 799.9343723081. The cubic root of 639895 is about 86.1726745176.

The spelling of 639895 in words is "six hundred thirty-nine thousand, eight hundred ninety-five".