639965 has 8 divisors (see below), whose sum is σ = 813240. Its totient is φ = 481792.

The previous prime is 639959. The next prime is 639983. The reversal of 639965 is 569936.

It can be written as a sum of positive squares in 4 ways, for example, as 89401 + 550564 = 299^2 + 742^2 .

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

It is a cyclic number.

It is not a de Polignac number, because 639965 - 2⁴ = 639949 is a prime.

It is a Curzon 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, 3680 + ... + 3849.

It is an arithmetic number, because the mean of its divisors is an integer number (101655).

2⁶³⁹⁹⁶⁵ is an apocalyptic number.

It is an amenable number.

639965 is a deficient number, since it is larger than the sum of its proper divisors (173275).

639965 is a wasteful number, since it uses less digits than its factorization.

639965 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7551.

The product of its digits is 43740, while the sum is 38.

The square root of 639965 is about 799.9781247009. The cubic root of 639965 is about 86.1758166307.

The spelling of 639965 in words is "six hundred thirty-nine thousand, nine hundred sixty-five".