399217728 has 224 divisors, whose sum is σ = 1322035456. Its totient is φ = 103514112.

The previous prime is 399217727. The next prime is 399217771. The reversal of 399217728 is 827712993.

It is a tau number, because it is divible by the number of its divisors (224).

It is a Harshad number since it is a multiple of its sum of digits (48).

It is not an unprimeable number, because it can be changed into a prime (399217727) by changing a digit.

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 31 ways as a sum of consecutive naturals, for example, 1275300 + ... + 1275612.

It is an arithmetic number, because the mean of its divisors is an integer number (5901944).

Almost surely, 2^399217728 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 399217728, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (661017728).

399217728 is an abundant number, since it is smaller than the sum of its proper divisors (922817728).

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

399217728 is a wasteful number, since it uses less digits than its factorization.

399217728 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 421 (or 411 counting only the distinct ones).

The product of its digits is 381024, while the sum is 48.

The square root of 399217728 is about 19980.4336289281. The cubic root of 399217728 is about 736.3256671559.

The spelling of 399217728 in words is "three hundred ninety-nine million, two hundred seventeen thousand, seven hundred twenty-eight".