399171991680 has 960 divisors, whose sum is σ = 1790926885440. Its totient is φ = 82935705600.

The previous prime is 399171991663. The next prime is 399171991739. The reversal of 399171991680 is 86199171993.

399171991680 is a `hidden beast` number, since 399 + 1 + 71 + 99 + 16 + 80 = 666.

It is a tau number, because it is divible by the number of its divisors (960).

It is a Harshad number since it is a multiple of its sum of digits (63).

It is an unprimeable number.

It is a polite number, since it can be written in 119 ways as a sum of consecutive naturals, for example, 43903935 + ... + 43913025.

It is an arithmetic number, because the mean of its divisors is an integer number (1865548839).

Almost surely, 2^399171991680 is an apocalyptic number.

399171991680 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 399171991680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (895463442720).

399171991680 is an abundant number, since it is smaller than the sum of its proper divisors (1391754893760).

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

399171991680 is a wasteful number, since it uses less digits than its factorization.

399171991680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9151 (or 9119 counting only the distinct ones).

The product of its (nonzero) digits is 6613488, while the sum is 63.

It can be divided in two parts, 39 and 9171991680, that added together give a palindrome (9171991719).

The spelling of 399171991680 in words is "three hundred ninety-nine billion, one hundred seventy-one million, nine hundred ninety-one thousand, six hundred eighty".