644435219873 has 2 divisors, whose sum is σ = 644435219874. Its totient is φ = 644435219872.

The previous prime is 644435219843. The next prime is 644435219881. The reversal of 644435219873 is 378912534446.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 502783101184 + 141652118689 = 709072^2 + 376367^2 .

It is a cyclic number.

It is not a de Polignac number, because 644435219873 - 2⁶ = 644435219809 is a prime.

It is a super-2 number, since 2×644435219873² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (644435219803) 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, 322217609936 + 322217609937.

It is an arithmetic number, because the mean of its divisors is an integer number (322217609937).

Almost surely, 2^644435219873 is an apocalyptic number.

It is an amenable number.

644435219873 is a deficient number, since it is larger than the sum of its proper divisors (1).

644435219873 is an equidigital number, since it uses as much as digits as its factorization.

644435219873 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 17418240, while the sum is 56.

The spelling of 644435219873 in words is "six hundred forty-four billion, four hundred thirty-five million, two hundred nineteen thousand, eight hundred seventy-three".