638841043649 has 2 divisors, whose sum is σ = 638841043650. Its totient is φ = 638841043648.

The previous prime is 638841043639. The next prime is 638841043679. The reversal of 638841043649 is 946340148836.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 495932850625 + 142908193024 = 704225^2 + 378032^2 .

It is a cyclic number.

It is not a de Polignac number, because 638841043649 - 2¹² = 638841039553 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 638841043594 and 638841043603.

It is not a weakly prime, because it can be changed into another prime (638841043639) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319420521824 + 319420521825.

It is an arithmetic number, because the mean of its divisors is an integer number (319420521825).

Almost surely, 2^638841043649 is an apocalyptic number.

It is an amenable number.

638841043649 is a deficient number, since it is larger than the sum of its proper divisors (1).

638841043649 is an equidigital number, since it uses as much as digits as its factorization.

638841043649 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11943936, while the sum is 56.

The spelling of 638841043649 in words is "six hundred thirty-eight billion, eight hundred forty-one million, forty-three thousand, six hundred forty-nine".