644404423656641 has 2 divisors, whose sum is σ = 644404423656642. Its totient is φ = 644404423656640.

The previous prime is 644404423656607. The next prime is 644404423656689. The reversal of 644404423656641 is 146656324404446.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 517275889690000 + 127128533966641 = 22743700^2 + 11275129^2 .

It is a cyclic number.

It is not a de Polignac number, because 644404423656641 - 2¹⁰ = 644404423655617 is a prime.

It is a super-2 number, since 2×644404423656641² (a number of 30 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (644404423676641) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322202211828320 + 322202211828321.

It is an arithmetic number, because the mean of its divisors is an integer number (322202211828321).

Almost surely, 2^{644404423656641} is an apocalyptic number.

It is an amenable number.

644404423656641 is a deficient number, since it is larger than the sum of its proper divisors (1).

644404423656641 is an equidigital number, since it uses as much as digits as its factorization.

644404423656641 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 159252480, while the sum is 59.

The spelling of 644404423656641 in words is "six hundred forty-four trillion, four hundred four billion, four hundred twenty-three million, six hundred fifty-six thousand, six hundred forty-one".