985991 has 2 divisors, whose sum is σ = 985992. Its totient is φ = 985990.

The previous prime is 985981. The next prime is 985993. The reversal of 985991 is 199589.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-985991 is a prime.

Together with 985993, 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 (985993) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 492995 + 492996.

It is an arithmetic number, because the mean of its divisors is an integer number (492996).

2⁹⁸⁵⁹⁹¹ is an apocalyptic number.

985991 is a deficient number, since it is larger than the sum of its proper divisors (1).

985991 is an equidigital number, since it uses as much as digits as its factorization.

985991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 29160, while the sum is 41.

The square root of 985991 is about 992.9707951395. The cubic root of 985991 is about 99.5308356236.

The spelling of 985991 in words is "nine hundred eighty-five thousand, nine hundred ninety-one".