644644213 has 2 divisors, whose sum is σ = 644644214. Its totient is φ = 644644212.

The previous prime is 644644201. The next prime is 644644289. The reversal of 644644213 is 312446446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 633931684 + 10712529 = 25178^2 + 3273^2 .

It is a cyclic number.

It is not a de Polignac number, because 644644213 - 2⁵ = 644644181 is a prime.

It is a super-2 number, since 2×644644213² = 831132322708778738, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644644313) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322322106 + 322322107.

It is an arithmetic number, because the mean of its divisors is an integer number (322322107).

Almost surely, 2^644644213 is an apocalyptic number.

It is an amenable number.

644644213 is a deficient number, since it is larger than the sum of its proper divisors (1).

644644213 is an equidigital number, since it uses as much as digits as its factorization.

644644213 is an evil number, because the sum of its binary digits is even.

The product of its digits is 55296, while the sum is 34.

The square root of 644644213 is about 25389.8446824710. The cubic root of 644644213 is about 863.8533652650.

The spelling of 644644213 in words is "six hundred forty-four million, six hundred forty-four thousand, two hundred thirteen".