638681320786 has 8 divisors (see below), whose sum is σ = 1014376215420. Its totient is φ = 300555915648.

The previous prime is 638681320777. The next prime is 638681320793. The reversal of 638681320786 is 687023186836.

638681320786 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in 2 ways, for example, as 628561966761 + 10119354025 = 792819^2 + 100595^2 .

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

It is a self number, because there is not a number n which added to its sum of digits gives 638681320786.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9392372331 + ... + 9392372398.

Almost surely, 2^638681320786 is an apocalyptic number.

638681320786 is a deficient number, since it is larger than the sum of its proper divisors (375694894634).

638681320786 is a wasteful number, since it uses less digits than its factorization.

638681320786 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 18784744748.

The product of its (nonzero) digits is 13934592, while the sum is 58.

The spelling of 638681320786 in words is "six hundred thirty-eight billion, six hundred eighty-one million, three hundred twenty thousand, seven hundred eighty-six".