639845 has 8 divisors (see below), whose sum is σ = 778776. Its totient is φ = 504576.

The previous prime is 639839. The next prime is 639851. The reversal of 639845 is 548936.

639845 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is an interprime number because it is at equal distance from previous prime (639839) and next prime (639851).

It can be written as a sum of positive squares in 4 ways, for example, as 1444 + 638401 = 38^2 + 799^2 .

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

It is not a de Polignac number, because 639845 - 2⁸ = 639589 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 512 + ... + 1241.

It is an arithmetic number, because the mean of its divisors is an integer number (97347).

2⁶³⁹⁸⁴⁵ is an apocalyptic number.

It is an amenable number.

639845 is a deficient number, since it is larger than the sum of its proper divisors (138931).

639845 is a wasteful number, since it uses less digits than its factorization.

639845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1831.

The product of its digits is 25920, while the sum is 35.

The square root of 639845 is about 799.9031191338. The cubic root of 639845 is about 86.1704300109.

Subtracting from 639845 its reverse (548936), we obtain a palindrome (90909).

The spelling of 639845 in words is "six hundred thirty-nine thousand, eight hundred forty-five".