399615840 has 144 divisors (see below), whose sum is σ = 1468657008. Its totient is φ = 98362368.

The previous prime is 399615829. The next prime is 399615859. The reversal of 399615840 is 48516993.

It is a happy number.

399615840 is a `hidden beast` number, since 3 + 9 + 9 + 61 + 584 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (144).

It is a Harshad number since it is a multiple of its sum of digits (45).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 8047 + ... + 29393.

It is an arithmetic number, because the mean of its divisors is an integer number (10199007).

Almost surely, 2^399615840 is an apocalyptic number.

399615840 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 399615840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (734328504).

399615840 is an abundant number, since it is smaller than the sum of its proper divisors (1069041168).

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

399615840 is a wasteful number, since it uses less digits than its factorization.

399615840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21381 (or 21370 counting only the distinct ones).

The product of its (nonzero) digits is 233280, while the sum is 45.

The square root of 399615840 is about 19990.3936929716. The cubic root of 399615840 is about 736.5703479192.

The spelling of 399615840 in words is "three hundred ninety-nine million, six hundred fifteen thousand, eight hundred forty".