639395678 has 4 divisors (see below), whose sum is σ = 959093520. Its totient is φ = 319697838.

The previous prime is 639395671. The next prime is 639395693. The reversal of 639395678 is 876593936.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639395671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 159848918 + ... + 159848921.

It is an arithmetic number, because the mean of its divisors is an integer number (239773380).

Almost surely, 2^639395678 is an apocalyptic number.

639395678 is a deficient number, since it is larger than the sum of its proper divisors (319697842).

639395678 is a wasteful number, since it uses less digits than its factorization.

639395678 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319697841.

The product of its digits is 7348320, while the sum is 56.

The square root of 639395678 is about 25286.2744982332. The cubic root of 639395678 is about 861.5025463684.

The spelling of 639395678 in words is "six hundred thirty-nine million, three hundred ninety-five thousand, six hundred seventy-eight".