399999840 has 96 divisors (see below), whose sum is σ = 1266886656. Its totient is φ = 106083840.

The previous prime is 399999839. The next prime is 399999857. The reversal of 399999840 is 48999993.

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

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 15 ways as a sum of consecutive naturals, for example, 89499 + ... + 93861.

It is an arithmetic number, because the mean of its divisors is an integer number (13196736).

Almost surely, 2^399999840 is an apocalyptic number.

399999840 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 399999840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (633443328).

399999840 is an abundant number, since it is smaller than the sum of its proper divisors (866886816).

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

399999840 is a wasteful number, since it uses less digits than its factorization.

399999840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4572 (or 4564 counting only the distinct ones).

The product of its (nonzero) digits is 5668704, while the sum is 60.

The square root of 399999840 is about 19999.9959999996. The cubic root of 399999840 is about 736.8062014872.

The spelling of 399999840 in words is "three hundred ninety-nine million, nine hundred ninety-nine thousand, eight hundred forty".