399121920 has 240 divisors, whose sum is σ = 1465017840. Its totient is φ = 100073472.

The previous prime is 399121913. The next prime is 399121927. The reversal of 399121920 is 29121993.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (399121913) and next prime (399121927).

It is a tau number, because it is divible by the number of its divisors (240).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (399121927) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 391171 + ... + 392189.

It is an arithmetic number, because the mean of its divisors is an integer number (6104241).

Almost surely, 2^399121920 is an apocalyptic number.

399121920 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 399121920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (732508920).

399121920 is an abundant number, since it is smaller than the sum of its proper divisors (1065895920).

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

399121920 is a wasteful number, since it uses less digits than its factorization.

399121920 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1065 (or 1046 counting only the distinct ones).

The product of its (nonzero) digits is 8748, while the sum is 36.

The square root of 399121920 is about 19978.0359395012. The cubic root of 399121920 is about 736.2667590056.

The spelling of 399121920 in words is "three hundred ninety-nine million, one hundred twenty-one thousand, nine hundred twenty".