638844866749 has 2 divisors, whose sum is σ = 638844866750. Its totient is φ = 638844866748.

The previous prime is 638844866717. The next prime is 638844866761. The reversal of 638844866749 is 947668448836.

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., 438873125625 + 199971741124 = 662475^2 + 447182^2 .

It is a cyclic number.

It is not a de Polignac number, because 638844866749 - 2⁵ = 638844866717 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638844566749) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319422433374 + 319422433375.

It is an arithmetic number, because the mean of its divisors is an integer number (319422433375).

Almost surely, 2^638844866749 is an apocalyptic number.

It is an amenable number.

638844866749 is a deficient number, since it is larger than the sum of its proper divisors (1).

638844866749 is an equidigital number, since it uses as much as digits as its factorization.

638844866749 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1337720832, while the sum is 73.

The spelling of 638844866749 in words is "six hundred thirty-eight billion, eight hundred forty-four million, eight hundred sixty-six thousand, seven hundred forty-nine".