644847493 has 2 divisors, whose sum is σ = 644847494. Its totient is φ = 644847492.

The previous prime is 644847491. The next prime is 644847503. The reversal of 644847493 is 394748446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 644042884 + 804609 = 25378^2 + 897^2 .

It is a cyclic number.

It is not a de Polignac number, because 644847493 - 2¹ = 644847491 is a prime.

Together with 644847491, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (644847491) 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, 322423746 + 322423747.

It is an arithmetic number, because the mean of its divisors is an integer number (322423747).

Almost surely, 2^644847493 is an apocalyptic number.

It is an amenable number.

644847493 is a deficient number, since it is larger than the sum of its proper divisors (1).

644847493 is an equidigital number, since it uses as much as digits as its factorization.

644847493 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2322432, while the sum is 49.

The square root of 644847493 is about 25393.8475422690. The cubic root of 644847493 is about 863.9441572883.

The spelling of 644847493 in words is "six hundred forty-four million, eight hundred forty-seven thousand, four hundred ninety-three".