639706 has 8 divisors (see below), whose sum is σ = 963540. Its totient is φ = 318528.

The previous prime is 639703. The next prime is 639713. The reversal of 639706 is 607936.

639706 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 2 ways, for example, as 555025 + 84681 = 745^2 + 291^2 .

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

It is a nialpdrome in base 15.

It is not an unprimeable number, because it can be changed into a prime (639701) 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, 130 + ... + 1138.

2⁶³⁹⁷⁰⁶ is an apocalyptic number.

639706 is a deficient number, since it is larger than the sum of its proper divisors (323834).

639706 is a wasteful number, since it uses less digits than its factorization.

639706 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1328.

The product of its (nonzero) digits is 6804, while the sum is 31.

The square root of 639706 is about 799.8162288926. The cubic root of 639706 is about 86.1641896677.

The spelling of 639706 in words is "six hundred thirty-nine thousand, seven hundred six".