646688213 has 2 divisors, whose sum is σ = 646688214. Its totient is φ = 646688212.

The previous prime is 646688201. The next prime is 646688227. The reversal of 646688213 is 312886646.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 638724529 + 7963684 = 25273^2 + 2822^2 .

It is a cyclic number.

It is not a de Polignac number, because 646688213 - 2⁶ = 646688149 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (646688293) 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, 323344106 + 323344107.

It is an arithmetic number, because the mean of its divisors is an integer number (323344107).

Almost surely, 2^646688213 is an apocalyptic number.

It is an amenable number.

646688213 is a deficient number, since it is larger than the sum of its proper divisors (1).

646688213 is an equidigital number, since it uses as much as digits as its factorization.

646688213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 331776, while the sum is 44.

The square root of 646688213 is about 25430.0651395155. The cubic root of 646688213 is about 864.7654204802.

The spelling of 646688213 in words is "six hundred forty-six million, six hundred eighty-eight thousand, two hundred thirteen".