639565 has 4 divisors (see below), whose sum is σ = 767484. Its totient is φ = 511648.

The previous prime is 639563. The next prime is 639571. The reversal of 639565 is 565936.

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

It can be written as a sum of positive squares in 2 ways, for example, as 281961 + 357604 = 531^2 + 598^2 .

It is a cyclic number.

It is not a de Polignac number, because 639565 - 2¹ = 639563 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 639565.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639563) 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, 63952 + ... + 63961.

It is an arithmetic number, because the mean of its divisors is an integer number (191871).

2⁶³⁹⁵⁶⁵ is an apocalyptic number.

It is an amenable number.

639565 is a deficient number, since it is larger than the sum of its proper divisors (127919).

639565 is a wasteful number, since it uses less digits than its factorization.

639565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 127918.

The product of its digits is 24300, while the sum is 34.

The square root of 639565 is about 799.7280787868. The cubic root of 639565 is about 86.1578586117.

The spelling of 639565 in words is "six hundred thirty-nine thousand, five hundred sixty-five".