638678561810 has 8 divisors (see below), whose sum is σ = 1149621411276. Its totient is φ = 255471424720.

The previous prime is 638678561809. The next prime is 638678561813. The reversal of 638678561810 is 18165876836.

It can be written as a sum of positive squares in 2 ways, for example, as 626932987681 + 11745574129 = 791791^2 + 108377^2 .

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

It is a super-2 number, since 2×638678561810² (a number of 24 digits) contains 22 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 638678561810.

It is not an unprimeable number, because it can be changed into a prime (638678561813) 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 in 3 ways as a sum of consecutive naturals, for example, 31933928081 + ... + 31933928100.

Almost surely, 2^638678561810 is an apocalyptic number.

638678561810 is a deficient number, since it is larger than the sum of its proper divisors (510942849466).

638678561810 is a wasteful number, since it uses less digits than its factorization.

638678561810 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 63867856188.

The product of its (nonzero) digits is 11612160, while the sum is 59.

The spelling of 638678561810 in words is "six hundred thirty-eight billion, six hundred seventy-eight million, five hundred sixty-one thousand, eight hundred ten".