639465809 has 2 divisors, whose sum is σ = 639465810. Its totient is φ = 639465808.

The previous prime is 639465793. The next prime is 639465811. The reversal of 639465809 is 908564936.

639465809 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 524547409 + 114918400 = 22903^2 + 10720^2 .

It is a cyclic number.

It is not a de Polignac number, because 639465809 - 2⁴ = 639465793 is a prime.

Together with 639465811, 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 (639465839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319732904 + 319732905.

It is an arithmetic number, because the mean of its divisors is an integer number (319732905).

Almost surely, 2^639465809 is an apocalyptic number.

It is an amenable number.

639465809 is a deficient number, since it is larger than the sum of its proper divisors (1).

639465809 is an equidigital number, since it uses as much as digits as its factorization.

639465809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1399680, while the sum is 50.

The square root of 639465809 is about 25287.6612006726. The cubic root of 639465809 is about 861.5340426851.

The spelling of 639465809 in words is "six hundred thirty-nine million, four hundred sixty-five thousand, eight hundred nine".