639996840 has 384 divisors, whose sum is σ = 2493504000. Its totient is φ = 142248960.

The previous prime is 639996809. The next prime is 639996871. The reversal of 639996840 is 48699936.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (639996809) and next prime (639996871).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 8767044 + ... + 8767116.

It is an arithmetic number, because the mean of its divisors is an integer number (6493500).

Almost surely, 2^639996840 is an apocalyptic number.

639996840 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 639996840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1246752000).

639996840 is an abundant number, since it is smaller than the sum of its proper divisors (1853507160).

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

639996840 is a wasteful number, since it uses less digits than its factorization.

639996840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 182 (or 161 counting only the distinct ones).

The product of its (nonzero) digits is 2519424, while the sum is 54.

The square root of 639996840 is about 25298.1588262862. The cubic root of 639996840 is about 861.7724576742.

The spelling of 639996840 in words is "six hundred thirty-nine million, nine hundred ninety-six thousand, eight hundred forty".