647720657 has 2 divisors, whose sum is σ = 647720658. Its totient is φ = 647720656.

The previous prime is 647720639. The next prime is 647720669. The reversal of 647720657 is 756027746.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 645109201 + 2611456 = 25399^2 + 1616^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-647720657 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (647720257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323860328 + 323860329.

It is an arithmetic number, because the mean of its divisors is an integer number (323860329).

Almost surely, 2^647720657 is an apocalyptic number.

It is an amenable number.

647720657 is a deficient number, since it is larger than the sum of its proper divisors (1).

647720657 is an equidigital number, since it uses as much as digits as its factorization.

647720657 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 493920, while the sum is 44.

The square root of 647720657 is about 25450.3567165570. The cubic root of 647720657 is about 865.2253779166.

The spelling of 647720657 in words is "six hundred forty-seven million, seven hundred twenty thousand, six hundred fifty-seven".