639855 has 24 divisors (see below), whose sum is σ = 1132560. Its totient is φ = 334080.

The previous prime is 639853. The next prime is 639857. The reversal of 639855 is 558936.

It is an interprime number because it is at equal distance from previous prime (639853) and next prime (639857).

It is not a de Polignac number, because 639855 - 2¹ = 639853 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639851) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 2535 + ... + 2775.

It is an arithmetic number, because the mean of its divisors is an integer number (47190).

2⁶³⁹⁸⁵⁵ is an apocalyptic number.

639855 is a deficient number, since it is larger than the sum of its proper divisors (492705).

639855 is a wasteful number, since it uses less digits than its factorization.

639855 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 311 (or 308 counting only the distinct ones).

The product of its digits is 32400, while the sum is 36.

The square root of 639855 is about 799.9093698664. The cubic root of 639855 is about 86.1708789216.

The spelling of 639855 in words is "six hundred thirty-nine thousand, eight hundred fifty-five".