644023138457 has 2 divisors, whose sum is σ = 644023138458. Its totient is φ = 644023138456.

The previous prime is 644023138403. The next prime is 644023138489. The reversal of 644023138457 is 754831320446.

644023138457 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 549346310041 + 94676828416 = 741179^2 + 307696^2 .

It is a cyclic number.

It is not a de Polignac number, because 644023138457 - 2⁶ = 644023138393 is a prime.

It is not a weakly prime, because it can be changed into another prime (644023138657) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322011569228 + 322011569229.

It is an arithmetic number, because the mean of its divisors is an integer number (322011569229).

Almost surely, 2^644023138457 is an apocalyptic number.

It is an amenable number.

644023138457 is a deficient number, since it is larger than the sum of its proper divisors (1).

644023138457 is an equidigital number, since it uses as much as digits as its factorization.

644023138457 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1935360, while the sum is 47.

The spelling of 644023138457 in words is "six hundred forty-four billion, twenty-three million, one hundred thirty-eight thousand, four hundred fifty-seven".