68139691 has 4 divisors (see below), whose sum is σ = 68676352. Its totient is φ = 67603032.

The previous prime is 68139679. The next prime is 68139703. The reversal of 68139691 is 19693186.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19693186 = 2 ⋅9846593.

It is an interprime number because it is at equal distance from previous prime (68139679) and next prime (68139703).

It is a cyclic number.

It is not a de Polignac number, because 68139691 - 2¹⁹ = 67615403 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (68139601) 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, 268140 + ... + 268393.

It is an arithmetic number, because the mean of its divisors is an integer number (17169088).

Almost surely, 2^68139691 is an apocalyptic number.

68139691 is a deficient number, since it is larger than the sum of its proper divisors (536661).

68139691 is a wasteful number, since it uses less digits than its factorization.

68139691 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 536660.

The product of its digits is 69984, while the sum is 43.

The square root of 68139691 is about 8254.6769167545. The cubic root of 68139691 is about 408.4448143574. Note that the first 3 decimals are identical.

The spelling of 68139691 in words is "sixty-eight million, one hundred thirty-nine thousand, six hundred ninety-one".