638794789 has 2 divisors, whose sum is σ = 638794790. Its totient is φ = 638794788.

The previous prime is 638794787. The next prime is 638794811. The reversal of 638794789 is 987497836.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 340956225 + 297838564 = 18465^2 + 17258^2 .

It is a cyclic number.

It is not a de Polignac number, because 638794789 - 2¹ = 638794787 is a prime.

Together with 638794787, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638794787) 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, 319397394 + 319397395.

It is an arithmetic number, because the mean of its divisors is an integer number (319397395).

Almost surely, 2^638794789 is an apocalyptic number.

It is an amenable number.

638794789 is a deficient number, since it is larger than the sum of its proper divisors (1).

638794789 is an equidigital number, since it uses as much as digits as its factorization.

638794789 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 18289152, while the sum is 61.

The square root of 638794789 is about 25274.3899827474. The cubic root of 638794789 is about 861.2325885160.

The spelling of 638794789 in words is "six hundred thirty-eight million, seven hundred ninety-four thousand, seven hundred eighty-nine".