721081709 has 2 divisors, whose sum is σ = 721081710. Its totient is φ = 721081708.

The previous prime is 721081693. The next prime is 721081721. The reversal of 721081709 is 907180127.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 562875625 + 158206084 = 23725^2 + 12578^2 .

It is a cyclic number.

It is not a de Polignac number, because 721081709 - 2⁴ = 721081693 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 (721081759) 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, 360540854 + 360540855.

It is an arithmetic number, because the mean of its divisors is an integer number (360540855).

Almost surely, 2^721081709 is an apocalyptic number.

It is an amenable number.

721081709 is a deficient number, since it is larger than the sum of its proper divisors (1).

721081709 is an equidigital number, since it uses as much as digits as its factorization.

721081709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 7056, while the sum is 35.

The square root of 721081709 is about 26852.9646221791. The cubic root of 721081709 is about 896.7295743344.

The spelling of 721081709 in words is "seven hundred twenty-one million, eighty-one thousand, seven hundred nine".