847991 has 2 divisors, whose sum is σ = 847992. Its totient is φ = 847990.

The previous prime is 847969. The next prime is 847993. The reversal of 847991 is 199748.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 847991 - 2¹⁸ = 585847 is a prime.

Together with 847993, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (847993) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 423995 + 423996.

It is an arithmetic number, because the mean of its divisors is an integer number (423996).

2⁸⁴⁷⁹⁹¹ is an apocalyptic number.

847991 is a deficient number, since it is larger than the sum of its proper divisors (1).

847991 is an equidigital number, since it uses as much as digits as its factorization.

847991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18144, while the sum is 38.

The square root of 847991 is about 920.8642679570. The cubic root of 847991 is about 94.6521349666.

The spelling of 847991 in words is "eight hundred forty-seven thousand, nine hundred ninety-one".