3999815820 has 576 divisors, whose sum is σ = 16555069440. Its totient is φ = 754790400.

The previous prime is 3999815801. The next prime is 3999815843. The reversal of 3999815820 is 285189993.

It is an unprimeable number.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 14234080 + ... + 14234360.

It is an arithmetic number, because the mean of its divisors is an integer number (28741440).

Almost surely, 2^3999815820 is an apocalyptic number.

3999815820 is a gapful number since it is divisible by the number (30) 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 3999815820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (8277534720).

3999815820 is an abundant number, since it is smaller than the sum of its proper divisors (12555253620).

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

3999815820 is a wasteful number, since it uses less digits than its factorization.

3999815820 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 406 (or 401 counting only the distinct ones).

The product of its (nonzero) digits is 1399680, while the sum is 54.

The square root of 3999815820 is about 63244.0971158574. The cubic root of 3999815820 is about 1587.3766876338.

The spelling of 3999815820 in words is "three billion, nine hundred ninety-nine million, eight hundred fifteen thousand, eight hundred twenty".