68981991 has 32 divisors (see below), whose sum is σ = 105380352. Its totient is φ = 39811200.

The previous prime is 68981987. The next prime is 68981993. The reversal of 68981991 is 19918986.

It is a happy number.

It is not a de Polignac number, because 68981991 - 2² = 68981987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (68981993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 46816 + ... + 48266.

It is an arithmetic number, because the mean of its divisors is an integer number (3293136).

Almost surely, 2^68981991 is an apocalyptic number.

68981991 is a deficient number, since it is larger than the sum of its proper divisors (36398361).

68981991 is a wasteful number, since it uses less digits than its factorization.

68981991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1543.

The product of its digits is 279936, while the sum is 51.

The square root of 68981991 is about 8305.5397777628. The cubic root of 68981991 is about 410.1209062417.

The spelling of 68981991 in words is "sixty-eight million, nine hundred eighty-one thousand, nine hundred ninety-one".