331081991 has 4 divisors (see below), whose sum is σ = 332031000. Its totient is φ = 330132984.

The previous prime is 331081979. The next prime is 331082051. The reversal of 331081991 is 199180133.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-331081991 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 (331081901) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 473981 + ... + 474678.

It is an arithmetic number, because the mean of its divisors is an integer number (83007750).

Almost surely, 2^331081991 is an apocalyptic number.

331081991 is a deficient number, since it is larger than the sum of its proper divisors (949009).

331081991 is an equidigital number, since it uses as much as digits as its factorization.

331081991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 949008.

The product of its (nonzero) digits is 5832, while the sum is 35.

The square root of 331081991 is about 18195.6585756053. The cubic root of 331081991 is about 691.7967531842.

The spelling of 331081991 in words is "three hundred thirty-one million, eighty-one thousand, nine hundred ninety-one".