639661380 has 48 divisors (see below), whose sum is σ = 1896410880. Its totient is φ = 160542208.

The previous prime is 639661367. The next prime is 639661387. The reversal of 639661380 is 83166936.

It is not an unprimeable number, because it can be changed into a prime (639661387) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 312540 + ... + 314579.

It is an arithmetic number, because the mean of its divisors is an integer number (39508560).

Almost surely, 2^639661380 is an apocalyptic number.

639661380 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

639661380 is an abundant number, since it is smaller than the sum of its proper divisors (1256749500).

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

639661380 is a wasteful number, since it uses less digits than its factorization.

639661380 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 627148 (or 627146 counting only the distinct ones).

The product of its (nonzero) digits is 139968, while the sum is 42.

The square root of 639661380 is about 25291.5278304811. The cubic root of 639661380 is about 861.6218628093.

It can be divided in two parts, 6396 and 61380, that added together give a palindrome (67776).

The spelling of 639661380 in words is "six hundred thirty-nine million, six hundred sixty-one thousand, three hundred eighty".