399666385 has 4 divisors (see below), whose sum is σ = 479599668. Its totient is φ = 319733104.

The previous prime is 399666373. The next prime is 399666389. The reversal of 399666385 is 583666993.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 313714944 + 85951441 = 17712^2 + 9271^2 .

It is a cyclic number.

It is not a de Polignac number, because 399666385 - 2²¹ = 397569233 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (399666389) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 39966634 + ... + 39966643.

It is an arithmetic number, because the mean of its divisors is an integer number (119899917).

Almost surely, 2^399666385 is an apocalyptic number.

It is an amenable number.

399666385 is a deficient number, since it is larger than the sum of its proper divisors (79933283).

399666385 is an equidigital number, since it uses as much as digits as its factorization.

399666385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79933282.

The product of its digits is 6298560, while the sum is 55.

The square root of 399666385 is about 19991.6578852280. The cubic root of 399666385 is about 736.6014013918.

The spelling of 399666385 in words is "three hundred ninety-nine million, six hundred sixty-six thousand, three hundred eighty-five".