639878400 has 648 divisors, whose sum is σ = 2803223360. Its totient is φ = 139898880.

The previous prime is 639878339. The next prime is 639878401. The reversal of 639878400 is 4878936.

It is a happy number.

639878400 is a `hidden beast` number, since 639 + 8 + 7 + 8 + 4 + 0 + 0 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (639878401) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 27820789 + ... + 27820811.

Almost surely, 2^639878400 is an apocalyptic number.

639878400 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 639878400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1401611680).

639878400 is an abundant number, since it is smaller than the sum of its proper divisors (2163344960).

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

639878400 is a wasteful number, since it uses less digits than its factorization.

639878400 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 88 (or 40 counting only the distinct ones).

The product of its (nonzero) digits is 290304, while the sum is 45.

The square root of 639878400 is about 25295.8178361562. The cubic root of 639878400 is about 861.7192935436.

The spelling of 639878400 in words is "six hundred thirty-nine million, eight hundred seventy-eight thousand, four hundred".