644513213 has 2 divisors, whose sum is σ = 644513214. Its totient is φ = 644513212.

The previous prime is 644513201. The next prime is 644513237. The reversal of 644513213 is 312315446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 644245924 + 267289 = 25382^2 + 517^2 .

It is a cyclic number.

It is not a de Polignac number, because 644513213 - 2¹⁰ = 644512189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644513273) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322256606 + 322256607.

It is an arithmetic number, because the mean of its divisors is an integer number (322256607).

Almost surely, 2^644513213 is an apocalyptic number.

It is an amenable number.

644513213 is a deficient number, since it is larger than the sum of its proper divisors (1).

644513213 is an equidigital number, since it uses as much as digits as its factorization.

644513213 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 8640, while the sum is 29.

The square root of 644513213 is about 25387.2647798064. The cubic root of 644513213 is about 863.7948459273.

Adding to 644513213 its reverse (312315446), we get a palindrome (956828659).

The spelling of 644513213 in words is "six hundred forty-four million, five hundred thirteen thousand, two hundred thirteen".