638353648781 has 8 divisors (see below), whose sum is σ = 640704485304. Its totient is φ = 636005877760.

The previous prime is 638353648753. The next prime is 638353648783. The reversal of 638353648781 is 187846353836.

It can be written as a sum of positive squares in 4 ways, for example, as 173080960900 + 465272687881 = 416030^2 + 682109^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 638353648781 - 2³⁰ = 637279906957 is a prime.

It is a super-2 number, since 2×638353648781² (a number of 24 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (638353648783) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 348716 + ... + 1182501.

It is an arithmetic number, because the mean of its divisors is an integer number (80088060663).

Almost surely, 2^638353648781 is an apocalyptic number.

It is an amenable number.

638353648781 is a deficient number, since it is larger than the sum of its proper divisors (2350836523).

638353648781 is a wasteful number, since it uses less digits than its factorization.

638353648781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1532751.

The product of its digits is 69672960, while the sum is 62.

The spelling of 638353648781 in words is "six hundred thirty-eight billion, three hundred fifty-three million, six hundred forty-eight thousand, seven hundred eighty-one".