399428640 has 288 divisors, whose sum is σ = 1546534080. Its totient is φ = 93063168.

The previous prime is 399428633. The next prime is 399428641. The reversal of 399428640 is 46824993.

It is a tau number, because it is divible by the number of its divisors (288).

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

It is not an unprimeable number, because it can be changed into a prime (399428641) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 355119 + ... + 356241.

It is an arithmetic number, because the mean of its divisors is an integer number (5369910).

Almost surely, 2^399428640 is an apocalyptic number.

399428640 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 399428640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (773267040).

399428640 is an abundant number, since it is smaller than the sum of its proper divisors (1147105440).

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

399428640 is a wasteful number, since it uses less digits than its factorization.

399428640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1176 (or 1165 counting only the distinct ones).

The product of its (nonzero) digits is 373248, while the sum is 45.

The square root of 399428640 is about 19985.7108955373. The cubic root of 399428640 is about 736.4553145197.

The spelling of 399428640 in words is "three hundred ninety-nine million, four hundred twenty-eight thousand, six hundred forty".