646785817 has 2 divisors, whose sum is σ = 646785818. Its totient is φ = 646785816.

The previous prime is 646785803. The next prime is 646785827. The reversal of 646785817 is 718587646.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 625800256 + 20985561 = 25016^2 + 4581^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-646785817 is a prime.

It is not a weakly prime, because it can be changed into another prime (646785827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323392908 + 323392909.

It is an arithmetic number, because the mean of its divisors is an integer number (323392909).

Almost surely, 2^646785817 is an apocalyptic number.

It is an amenable number.

646785817 is a deficient number, since it is larger than the sum of its proper divisors (1).

646785817 is an equidigital number, since it uses as much as digits as its factorization.

646785817 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2257920, while the sum is 52.

The square root of 646785817 is about 25431.9841341567. The cubic root of 646785817 is about 864.8089243493.

The spelling of 646785817 in words is "six hundred forty-six million, seven hundred eighty-five thousand, eight hundred seventeen".