644851763617 has 2 divisors, whose sum is σ = 644851763618. Its totient is φ = 644851763616.

The previous prime is 644851763603. The next prime is 644851763641. The reversal of 644851763617 is 716367158446.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 372168323136 + 272683440481 = 610056^2 + 522191^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-644851763617 is a prime.

It is not a weakly prime, because it can be changed into another prime (644851763417) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322425881808 + 322425881809.

It is an arithmetic number, because the mean of its divisors is an integer number (322425881809).

Almost surely, 2^644851763617 is an apocalyptic number.

It is an amenable number.

644851763617 is a deficient number, since it is larger than the sum of its proper divisors (1).

644851763617 is an equidigital number, since it uses as much as digits as its factorization.

644851763617 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20321280, while the sum is 58.

The spelling of 644851763617 in words is "six hundred forty-four billion, eight hundred fifty-one million, seven hundred sixty-three thousand, six hundred seventeen".