399209940 has 144 divisors (see below), whose sum is σ = 1293626880. Its totient is φ = 99429120.

The previous prime is 399209927. The next prime is 399209947. The reversal of 399209940 is 49902993.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399209947) 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, 160587 + ... + 163053.

It is an arithmetic number, because the mean of its divisors is an integer number (8983520).

Almost surely, 2^399209940 is an apocalyptic number.

399209940 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 399209940, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (646813440).

399209940 is an abundant number, since it is smaller than the sum of its proper divisors (894416940).

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

399209940 is a wasteful number, since it uses less digits than its factorization.

399209940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2542 (or 2537 counting only the distinct ones).

The product of its (nonzero) digits is 157464, while the sum is 45.

The square root of 399209940 is about 19980.2387373124. The cubic root of 399209940 is about 736.3208790071.

The spelling of 399209940 in words is "three hundred ninety-nine million, two hundred nine thousand, nine hundred forty".