399689 has 2 divisors, whose sum is σ = 399690. Its totient is φ = 399688.

The previous prime is 399677. The next prime is 399691. The reversal of 399689 is 986993.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 284089 + 115600 = 533^2 + 340^2 .

It is a cyclic number.

It is not a de Polignac number, because 399689 - 2⁸ = 399433 is a prime.

Together with 399691, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (399389) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 199844 + 199845.

It is an arithmetic number, because the mean of its divisors is an integer number (199845).

2³⁹⁹⁶⁸⁹ is an apocalyptic number.

It is an amenable number.

399689 is a deficient number, since it is larger than the sum of its proper divisors (1).

399689 is an equidigital number, since it uses as much as digits as its factorization.

399689 is an evil number, because the sum of its binary digits is even.

The product of its digits is 104976, while the sum is 44.

The square root of 399689 is about 632.2096171366. The cubic root of 399689 is about 73.6615294585.

It can be divided in two parts, 399 and 689, that multiplied together give a triangular number (274911 = T₇₄₁).

The spelling of 399689 in words is "three hundred ninety-nine thousand, six hundred eighty-nine".