1991443 has 2 divisors, whose sum is σ = 1991444. Its totient is φ = 1991442.

The previous prime is 1991413. The next prime is 1991449. The reversal of 1991443 is 3441991.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1991443 is a prime.

It is not a weakly prime, because it can be changed into another prime (1991449) by changing a digit.

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

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 995721 + 995722.

It is an arithmetic number, because the mean of its divisors is an integer number (995722).

2^1991443 is an apocalyptic number.

1991443 is a deficient number, since it is larger than the sum of its proper divisors (1).

1991443 is an equidigital number, since it uses as much as digits as its factorization.

1991443 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3888, while the sum is 31.

The square root of 1991443 is about 1411.1849630718. The cubic root of 1991443 is about 125.8121623764.

The spelling of 1991443 in words is "one million, nine hundred ninety-one thousand, four hundred forty-three".