390809 has 2 divisors, whose sum is σ = 390810. Its totient is φ = 390808.

The previous prime is 390791. The next prime is 390821. The reversal of 390809 is 908093.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 270400 + 120409 = 520^2 + 347^2 .

It is a cyclic number.

It is not a de Polignac number, because 390809 - 2⁸ = 390553 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a plaindrome in base 15.

It is not a weakly prime, because it can be changed into another prime (390829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195404 + 195405.

It is an arithmetic number, because the mean of its divisors is an integer number (195405).

2³⁹⁰⁸⁰⁹ is an apocalyptic number.

It is an amenable number.

390809 is a deficient number, since it is larger than the sum of its proper divisors (1).

390809 is an equidigital number, since it uses as much as digits as its factorization.

390809 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 29.

The square root of 390809 is about 625.1471826698. The cubic root of 390809 is about 73.1119193979. Note that the first 3 decimals are identical.

The spelling of 390809 in words is "three hundred ninety thousand, eight hundred nine".