642896909 has 2 divisors, whose sum is σ = 642896910. Its totient is φ = 642896908.

The previous prime is 642896899. The next prime is 642896921. The reversal of 642896909 is 909698246.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 591559684 + 51337225 = 24322^2 + 7165^2 .

It is a cyclic number.

It is not a de Polignac number, because 642896909 - 2²⁴ = 626119693 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (642895909) 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, 321448454 + 321448455.

It is an arithmetic number, because the mean of its divisors is an integer number (321448455).

Almost surely, 2^642896909 is an apocalyptic number.

It is an amenable number.

642896909 is a deficient number, since it is larger than the sum of its proper divisors (1).

642896909 is an equidigital number, since it uses as much as digits as its factorization.

642896909 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1679616, while the sum is 53.

The square root of 642896909 is about 25355.4118286412. The cubic root of 642896909 is about 863.0721693639.

The spelling of 642896909 in words is "six hundred forty-two million, eight hundred ninety-six thousand, nine hundred nine".