8491391 has 2 divisors, whose sum is σ = 8491392. Its totient is φ = 8491390.

The previous prime is 8491369. The next prime is 8491409. The reversal of 8491391 is 1931948.

8491391 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8491391 is a prime.

It is a super-2 number, since 2×8491391² = 144207442229762, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (8491321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4245695 + 4245696.

It is an arithmetic number, because the mean of its divisors is an integer number (4245696).

Almost surely, 2^8491391 is an apocalyptic number.

8491391 is a deficient number, since it is larger than the sum of its proper divisors (1).

8491391 is an equidigital number, since it uses as much as digits as its factorization.

8491391 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7776, while the sum is 35.

The square root of 8491391 is about 2913.9991420726. Note that the first 3 decimals coincide. The cubic root of 8491391 is about 204.0138318828.

The spelling of 8491391 in words is "eight million, four hundred ninety-one thousand, three hundred ninety-one".