644259265537 has 2 divisors, whose sum is σ = 644259265538. Its totient is φ = 644259265536.

The previous prime is 644259265523. The next prime is 644259265549. The reversal of 644259265537 is 735562952446.

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., 533928335616 + 110330929921 = 730704^2 + 332161^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644259265537 is a prime.

It is not a weakly prime, because it can be changed into another prime (644259265567) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322129632768 + 322129632769.

It is an arithmetic number, because the mean of its divisors is an integer number (322129632769).

Almost surely, 2^644259265537 is an apocalyptic number.

It is an amenable number.

644259265537 is a deficient number, since it is larger than the sum of its proper divisors (1).

644259265537 is an equidigital number, since it uses as much as digits as its factorization.

644259265537 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 54432000, while the sum is 58.

The spelling of 644259265537 in words is "six hundred forty-four billion, two hundred fifty-nine million, two hundred sixty-five thousand, five hundred thirty-seven".