639859878 has 64 divisors (see below), whose sum is σ = 1630187520. Its totient is φ = 182238336.

The previous prime is 639859873. The next prime is 639859919. The reversal of 639859878 is 878958936.

639859878 is a `hidden beast` number, since 6 + 39 + 8 + 598 + 7 + 8 = 666.

639859878 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639859873) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 124875 + ... + 129897.

It is an arithmetic number, because the mean of its divisors is an integer number (25471680).

Almost surely, 2^639859878 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639859878, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (815093760).

639859878 is an abundant number, since it is smaller than the sum of its proper divisors (990327642).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

639859878 is a wasteful number, since it uses less digits than its factorization.

639859878 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5378 (or 5372 counting only the distinct ones).

The product of its digits is 26127360, while the sum is 63.

The square root of 639859878 is about 25295.4517255573. The cubic root of 639859878 is about 861.7109789853.

The spelling of 639859878 in words is "six hundred thirty-nine million, eight hundred fifty-nine thousand, eight hundred seventy-eight".