12931991 has 4 divisors (see below), whose sum is σ = 13349184. Its totient is φ = 12514800.

The previous prime is 12931987. The next prime is 12932021. The reversal of 12931991 is 19913921.

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

It is a cyclic number.

It is not a de Polignac number, because 12931991 - 2² = 12931987 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 (12931921) 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 3 ways as a sum of consecutive naturals, for example, 208550 + ... + 208611.

It is an arithmetic number, because the mean of its divisors is an integer number (3337296).

Almost surely, 2^12931991 is an apocalyptic number.

12931991 is a deficient number, since it is larger than the sum of its proper divisors (417193).

12931991 is an equidigital number, since it uses as much as digits as its factorization.

12931991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 417192.

The product of its digits is 4374, while the sum is 35.

The square root of 12931991 is about 3596.1077570062. The cubic root of 12931991 is about 234.7227211009.

The spelling of 12931991 in words is "twelve million, nine hundred thirty-one thousand, nine hundred ninety-one".