639216709 has 2 divisors, whose sum is σ = 639216710. Its totient is φ = 639216708.

The previous prime is 639216653. The next prime is 639216731. The reversal of 639216709 is 907612936.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 590635809 + 48580900 = 24303^2 + 6970^2 .

It is a cyclic number.

It is not a de Polignac number, because 639216709 - 2⁷ = 639216581 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (639216749) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319608354 + 319608355.

It is an arithmetic number, because the mean of its divisors is an integer number (319608355).

Almost surely, 2^639216709 is an apocalyptic number.

It is an amenable number.

639216709 is a deficient number, since it is larger than the sum of its proper divisors (1).

639216709 is an equidigital number, since it uses as much as digits as its factorization.

639216709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 122472, while the sum is 43.

The square root of 639216709 is about 25282.7353939403. The cubic root of 639216709 is about 861.4221597147.

The spelling of 639216709 in words is "six hundred thirty-nine million, two hundred sixteen thousand, seven hundred nine".