3991331 has 2 divisors, whose sum is σ = 3991332. Its totient is φ = 3991330.

The previous prime is 3991321. The next prime is 3991333. The reversal of 3991331 is 1331993.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 3991331 - 2¹⁰ = 3990307 is a prime.

It is a super-2 number, since 2×3991331² = 31861446303122, which contains 22 as substring.

Together with 3991333, it forms a pair of twin primes.

It is a Chen prime.

It is an Ulam number.

It is a junction number, because it is equal to n+sod(n) for n = 3991294 and 3991303.

It is not a weakly prime, because it can be changed into another prime (3991333) 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 as a sum of consecutive naturals, namely, 1995665 + 1995666.

It is an arithmetic number, because the mean of its divisors is an integer number (1995666).

Almost surely, 2^3991331 is an apocalyptic number.

3991331 is a deficient number, since it is larger than the sum of its proper divisors (1).

3991331 is an equidigital number, since it uses as much as digits as its factorization.

3991331 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2187, while the sum is 29.

The square root of 3991331 is about 1997.8315744827. The cubic root of 3991331 is about 158.6253457551.

The spelling of 3991331 in words is "three million, nine hundred ninety-one thousand, three hundred thirty-one".