399666389 has 2 divisors, whose sum is σ = 399666390. Its totient is φ = 399666388.

The previous prime is 399666373. The next prime is 399666391. The reversal of 399666389 is 983666993.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 226954225 + 172712164 = 15065^2 + 13142^2 .

It is a cyclic number.

It is not a de Polignac number, because 399666389 - 2⁴ = 399666373 is a prime.

Together with 399666391, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (399666689) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199833194 + 199833195.

It is an arithmetic number, because the mean of its divisors is an integer number (199833195).

Almost surely, 2^399666389 is an apocalyptic number.

It is an amenable number.

399666389 is a deficient number, since it is larger than the sum of its proper divisors (1).

399666389 is an equidigital number, since it uses as much as digits as its factorization.

399666389 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 11337408, while the sum is 59.

The square root of 399666389 is about 19991.6579852698. The cubic root of 399666389 is about 736.6014038492.

The spelling of 399666389 in words is "three hundred ninety-nine million, six hundred sixty-six thousand, three hundred eighty-nine".