644045540513 has 2 divisors, whose sum is σ = 644045540514. Its totient is φ = 644045540512.

The previous prime is 644045540407. The next prime is 644045540531. The reversal of 644045540513 is 315045540446.

Together with next prime (644045540531) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 644019090064 + 26450449 = 802508^2 + 5143^2 .

It is a cyclic number.

It is not a de Polignac number, because 644045540513 - 2³⁴ = 626865671329 is a prime.

It is not a weakly prime, because it can be changed into another prime (644045540543) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322022770256 + 322022770257.

It is an arithmetic number, because the mean of its divisors is an integer number (322022770257).

Almost surely, 2^644045540513 is an apocalyptic number.

It is an amenable number.

644045540513 is a deficient number, since it is larger than the sum of its proper divisors (1).

644045540513 is an equidigital number, since it uses as much as digits as its factorization.

644045540513 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576000, while the sum is 41.

The spelling of 644045540513 in words is "six hundred forty-four billion, forty-five million, five hundred forty thousand, five hundred thirteen".