644398217 has 2 divisors, whose sum is σ = 644398218. Its totient is φ = 644398216.

The previous prime is 644398211. The next prime is 644398231. The reversal of 644398217 is 712893446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 370793536 + 273604681 = 19256^2 + 16541^2 .

It is a cyclic number.

It is not a de Polignac number, because 644398217 - 2¹⁴ = 644381833 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (644398211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322199108 + 322199109.

It is an arithmetic number, because the mean of its divisors is an integer number (322199109).

Almost surely, 2^644398217 is an apocalyptic number.

It is an amenable number.

644398217 is a deficient number, since it is larger than the sum of its proper divisors (1).

644398217 is an equidigital number, since it uses as much as digits as its factorization.

644398217 is an evil number, because the sum of its binary digits is even.

The product of its digits is 290304, while the sum is 44.

The square root of 644398217 is about 25384.9998424266. Note that the first 3 decimals coincide. The cubic root of 644398217 is about 863.7434692405.

The spelling of 644398217 in words is "six hundred forty-four million, three hundred ninety-eight thousand, two hundred seventeen".