639841978 has 16 divisors (see below), whose sum is σ = 987250176. Its totient is φ = 310836960.

The previous prime is 639841933. The next prime is 639841981. The reversal of 639841978 is 879148936.

639841978 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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, 3051 + ... + 35902.

It is an arithmetic number, because the mean of its divisors is an integer number (61703136).

Almost surely, 2^639841978 is an apocalyptic number.

639841978 is a deficient number, since it is larger than the sum of its proper divisors (347408198).

639841978 is a wasteful number, since it uses less digits than its factorization.

639841978 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 39189.

The product of its digits is 2612736, while the sum is 55.

The square root of 639841978 is about 25295.0979045348. The cubic root of 639841978 is about 861.7029434914.

The spelling of 639841978 in words is "six hundred thirty-nine million, eight hundred forty-one thousand, nine hundred seventy-eight".