720731309 has 2 divisors, whose sum is σ = 720731310. Its totient is φ = 720731308.

The previous prime is 720731281. The next prime is 720731311. The reversal of 720731309 is 903137027.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 720654025 + 77284 = 26845^2 + 278^2 .

It is a cyclic number.

It is not a de Polignac number, because 720731309 - 2²⁴ = 703954093 is a prime.

It is a Sophie Germain prime.

Together with 720731311, it forms a pair of twin primes.

It is a Chen 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 (720739309) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360365654 + 360365655.

It is an arithmetic number, because the mean of its divisors is an integer number (360365655).

Almost surely, 2^720731309 is an apocalyptic number.

It is an amenable number.

720731309 is a deficient number, since it is larger than the sum of its proper divisors (1).

720731309 is an equidigital number, since it uses as much as digits as its factorization.

720731309 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7938, while the sum is 32.

The square root of 720731309 is about 26846.4394100968. The cubic root of 720731309 is about 896.5842995577.

The spelling of 720731309 in words is "seven hundred twenty million, seven hundred thirty-one thousand, three hundred nine".