639843 has 4 divisors (see below), whose sum is σ = 853128. Its totient is φ = 426560.

The previous prime is 639839. The next prime is 639851. The reversal of 639843 is 348936.

639843 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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 639843 - 2² = 639839 is a prime.

It is a D-number.

It is not an unprimeable number, because it can be changed into a prime (639833) 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, 106638 + ... + 106643.

It is an arithmetic number, because the mean of its divisors is an integer number (213282).

2⁶³⁹⁸⁴³ is an apocalyptic number.

639843 is a deficient number, since it is larger than the sum of its proper divisors (213285).

639843 is a wasteful number, since it uses less digits than its factorization.

639843 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 213284.

The product of its digits is 15552, while the sum is 33.

The square root of 639843 is about 799.9018689814. The cubic root of 639843 is about 86.1703402282.

It can be divided in two parts, 6398 and 43, that added together give a triangular number (6441 = T₁₁₃).

The spelling of 639843 in words is "six hundred thirty-nine thousand, eight hundred forty-three".