639439085 has 4 divisors (see below), whose sum is σ = 767326908. Its totient is φ = 511551264.

The previous prime is 639439081. The next prime is 639439121. The reversal of 639439085 is 580934936.

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 458859241 + 180579844 = 21421^2 + 13438^2 .

It is a cyclic number.

It is not a de Polignac number, because 639439085 - 2² = 639439081 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639439081) 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, 63943904 + ... + 63943913.

It is an arithmetic number, because the mean of its divisors is an integer number (191831727).

Almost surely, 2^639439085 is an apocalyptic number.

It is an amenable number.

639439085 is a deficient number, since it is larger than the sum of its proper divisors (127887823).

639439085 is a wasteful number, since it uses less digits than its factorization.

639439085 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 127887822.

The product of its (nonzero) digits is 699840, while the sum is 47.

The square root of 639439085 is about 25287.1327951589. The cubic root of 639439085 is about 861.5220410236.

The spelling of 639439085 in words is "six hundred thirty-nine million, four hundred thirty-nine thousand, eighty-five".