646664813 has 2 divisors, whose sum is σ = 646664814. Its totient is φ = 646664812.

The previous prime is 646664783. The next prime is 646664827. The reversal of 646664813 is 318466646.

646664813 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 643028164 + 3636649 = 25358^2 + 1907^2 .

It is a cyclic number.

It is not a de Polignac number, because 646664813 - 2¹⁶ = 646599277 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646664413) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 323332406 + 323332407.

It is an arithmetic number, because the mean of its divisors is an integer number (323332407).

Almost surely, 2^646664813 is an apocalyptic number.

It is an amenable number.

646664813 is a deficient number, since it is larger than the sum of its proper divisors (1).

646664813 is an equidigital number, since it uses as much as digits as its factorization.

646664813 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 497664, while the sum is 44.

The square root of 646664813 is about 25429.6050500199. The cubic root of 646664813 is about 864.7549900262.

The spelling of 646664813 in words is "six hundred forty-six million, six hundred sixty-four thousand, eight hundred thirteen".