399665988 has 216 divisors, whose sum is σ = 1188244512. Its totient is φ = 117013248.

The previous prime is 399665983. The next prime is 399665993. The reversal of 399665988 is 889566993.

399665988 is a `hidden beast` number, since 39 + 9 + 6 + 6 + 598 + 8 = 666.

It is an interprime number because it is at equal distance from previous prime (399665983) and next prime (399665993).

It is a super-2 number, since 2×399665988² = 319465803928032288, which contains 22 as substring.

Its product of digits (25194240) is a multiple of the sum of its prime divisors (108).

It is not an unprimeable number, because it can be changed into a prime (399665983) by changing a digit.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 5965131 + ... + 5965197.

It is an arithmetic number, because the mean of its divisors is an integer number (5501132).

Almost surely, 2^399665988 is an apocalyptic number.

399665988 is a gapful number since it is divisible by the number (38) 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 399665988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (594122256).

399665988 is an abundant number, since it is smaller than the sum of its proper divisors (788578524).

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

399665988 is a wasteful number, since it uses less digits than its factorization.

399665988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 141 (or 108 counting only the distinct ones).

The product of its digits is 25194240, while the sum is 63.

The square root of 399665988 is about 19991.6479560841. The cubic root of 399665988 is about 736.6011574960.

It can be divided in two parts, 39966 and 5988, that added together give a palindrome (45954).

The spelling of 399665988 in words is "three hundred ninety-nine million, six hundred sixty-five thousand, nine hundred eighty-eight".