639831840 has 96 divisors (see below), whose sum is σ = 2121577920. Its totient is φ = 161639424.

The previous prime is 639831827. The next prime is 639831979. The reversal of 639831840 is 48138936.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (96).

It is a junction number, because it is equal to n+sod(n) for n = 639831792 and 639831801.

It is an unprimeable number.

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, 25959 + ... + 44198.

It is an arithmetic number, because the mean of its divisors is an integer number (22099770).

Almost surely, 2^639831840 is an apocalyptic number.

639831840 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

639831840 is an abundant number, since it is smaller than the sum of its proper divisors (1481746080).

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

639831840 is a wasteful number, since it uses less digits than its factorization.

639831840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 70194 (or 70186 counting only the distinct ones).

The product of its (nonzero) digits is 124416, while the sum is 42.

The square root of 639831840 is about 25294.8975091816. The cubic root of 639831840 is about 861.6983923726.

The spelling of 639831840 in words is "six hundred thirty-nine million, eight hundred thirty-one thousand, eight hundred forty".