68139820681 has 4 divisors (see below), whose sum is σ = 70489469700. Its totient is φ = 65790171664.

The previous prime is 68139820627. The next prime is 68139820703. The reversal of 68139820681 is 18602893186.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 40103667081 + 28036153600 = 200259^2 + 167440^2 .

It is a cyclic number.

It is not a de Polignac number, because 68139820681 - 2²³ = 68131432073 is a prime.

It is a super-2 number, since 2×68139820681² (a number of 22 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (68139820081) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1174824466 + ... + 1174824523.

It is an arithmetic number, because the mean of its divisors is an integer number (17622367425).

Almost surely, 2^68139820681 is an apocalyptic number.

It is an amenable number.

68139820681 is a deficient number, since it is larger than the sum of its proper divisors (2349649019).

68139820681 is a wasteful number, since it uses less digits than its factorization.

68139820681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2349649018.

The product of its (nonzero) digits is 995328, while the sum is 52.

The spelling of 68139820681 in words is "sixty-eight billion, one hundred thirty-nine million, eight hundred twenty thousand, six hundred eighty-one".