68139661 has 4 divisors (see below), whose sum is σ = 68258332. Its totient is φ = 68020992.

The previous prime is 68139611. The next prime is 68139667. The reversal of 68139661 is 16693186.

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 35581225 + 32558436 = 5965^2 + 5706^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-68139661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (68139667) 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, 58470 + ... + 59623.

It is an arithmetic number, because the mean of its divisors is an integer number (17064583).

Almost surely, 2^68139661 is an apocalyptic number.

It is an amenable number.

68139661 is a deficient number, since it is larger than the sum of its proper divisors (118671).

68139661 is a wasteful number, since it uses less digits than its factorization.

68139661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 118670.

The product of its digits is 46656, while the sum is 40.

The square root of 68139661 is about 8254.6750996026. The cubic root of 68139661 is about 408.4447544151. Note that the first 3 decimals are identical.

The spelling of 68139661 in words is "sixty-eight million, one hundred thirty-nine thousand, six hundred sixty-one".