68211991 has 4 divisors (see below), whose sum is σ = 68279184. Its totient is φ = 68144800.

The previous prime is 68211967. The next prime is 68212009. The reversal of 68211991 is 19911286.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 19911286 = 2 ⋅9955643.

It is a cyclic number.

It is not a de Polignac number, because 68211991 - 2¹⁹ = 67687703 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 68211991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (68211931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 32050 + ... + 34111.

It is an arithmetic number, because the mean of its divisors is an integer number (17069796).

Almost surely, 2^68211991 is an apocalyptic number.

68211991 is a deficient number, since it is larger than the sum of its proper divisors (67193).

68211991 is a wasteful number, since it uses less digits than its factorization.

68211991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 67192.

The product of its digits is 7776, while the sum is 37.

The square root of 68211991 is about 8259.0550912317. The cubic root of 68211991 is about 408.5892241783.

The spelling of 68211991 in words is "sixty-eight million, two hundred eleven thousand, nine hundred ninety-one".