644045540531 has 2 divisors, whose sum is σ = 644045540532. Its totient is φ = 644045540530.

The previous prime is 644045540513. The next prime is 644045540543. The reversal of 644045540531 is 135045540446.

644045540531 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

Together with previous prime (644045540513) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 644045540531 - 2¹⁰ = 644045539507 is a prime.

It is a super-2 number, since 2×644045540531² (a number of 24 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (644045540581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322022770265 + 322022770266.

It is an arithmetic number, because the mean of its divisors is an integer number (322022770266).

Almost surely, 2^644045540531 is an apocalyptic number.

644045540531 is a deficient number, since it is larger than the sum of its proper divisors (1).

644045540531 is an equidigital number, since it uses as much as digits as its factorization.

644045540531 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 644045540531 in words is "six hundred forty-four billion, forty-five million, five hundred forty thousand, five hundred thirty-one".