638909863 has 2 divisors, whose sum is σ = 638909864. Its totient is φ = 638909862.

The previous prime is 638909849. The next prime is 638909897. The reversal of 638909863 is 368909836.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-638909863 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 638909863.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (638909813) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 319454931 + 319454932.

It is an arithmetic number, because the mean of its divisors is an integer number (319454932).

Almost surely, 2^638909863 is an apocalyptic number.

638909863 is a deficient number, since it is larger than the sum of its proper divisors (1).

638909863 is an equidigital number, since it uses as much as digits as its factorization.

638909863 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1679616, while the sum is 52.

The square root of 638909863 is about 25276.6663743461. Note that the first 3 decimals coincide. The cubic root of 638909863 is about 861.2843002342.

The spelling of 638909863 in words is "six hundred thirty-eight million, nine hundred nine thousand, eight hundred sixty-three".