639405 has 24 divisors (see below), whose sum is σ = 1194648. Its totient is φ = 314496.

The previous prime is 639391. The next prime is 639433. The reversal of 639405 is 504936.

It is a happy number.

639405 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 4 ways, for example, as 125316 + 514089 = 354^2 + 717^2 .

It is not a de Polignac number, because 639405 - 2⁹ = 638893 is a prime.

It is a Curzon number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 639405.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 39 + ... + 1131.

It is an arithmetic number, because the mean of its divisors is an integer number (49777).

2⁶³⁹⁴⁰⁵ is an apocalyptic number.

639405 is a gapful number since it is divisible by the number (65) formed by its first and last digit.

It is an amenable number.

639405 is a deficient number, since it is larger than the sum of its proper divisors (555243).

639405 is a wasteful number, since it uses less digits than its factorization.

639405 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1117 (or 1114 counting only the distinct ones).

The product of its (nonzero) digits is 3240, while the sum is 27.

The square root of 639405 is about 799.6280385279. The cubic root of 639405 is about 86.1506733076.

The spelling of 639405 in words is "six hundred thirty-nine thousand, four hundred five".