644901193 has 2 divisors, whose sum is σ = 644901194. Its totient is φ = 644901192.

The previous prime is 644901181. The next prime is 644901223. The reversal of 644901193 is 391109446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 349989264 + 294911929 = 18708^2 + 17173^2 .

It is a cyclic number.

It is not a de Polignac number, because 644901193 - 2⁹ = 644900681 is a prime.

It is not a weakly prime, because it can be changed into another prime (644904193) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322450596 + 322450597.

It is an arithmetic number, because the mean of its divisors is an integer number (322450597).

Almost surely, 2^644901193 is an apocalyptic number.

It is an amenable number.

644901193 is a deficient number, since it is larger than the sum of its proper divisors (1).

644901193 is an equidigital number, since it uses as much as digits as its factorization.

644901193 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23328, while the sum is 37.

The square root of 644901193 is about 25394.9048629838. The cubic root of 644901193 is about 863.9681384177.

The spelling of 644901193 in words is "six hundred forty-four million, nine hundred one thousand, one hundred ninety-three".