639442665780 has 96 divisors (see below), whose sum is σ = 1836375988608. Its totient is φ = 166153420800.

The previous prime is 639442665779. The next prime is 639442665811. The reversal of 639442665780 is 87566244936.

It is a Harshad number since it is a multiple of its sum of digits (60).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1834804 + ... + 2155316.

It is an arithmetic number, because the mean of its divisors is an integer number (19128916548).

Almost surely, 2^639442665780 is an apocalyptic number.

639442665780 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 639442665780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (918187994304).

639442665780 is an abundant number, since it is smaller than the sum of its proper divisors (1196933322828).

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

639442665780 is a wasteful number, since it uses less digits than its factorization.

639442665780 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 321377 (or 321375 counting only the distinct ones).

The product of its (nonzero) digits is 52254720, while the sum is 60.

The spelling of 639442665780 in words is "six hundred thirty-nine billion, four hundred forty-two million, six hundred sixty-five thousand, seven hundred eighty".