1991943 has 6 divisors (see below), whose sum is σ = 2877264. Its totient is φ = 1327956.

The previous prime is 1991933. The next prime is 1991947. The reversal of 1991943 is 3491991.

It is not a de Polignac number, because 1991943 - 2⁵ = 1991911 is a prime.

1991943 is a lucky number.

It is a junction number, because it is equal to n+sod(n) for n = 1991898 and 1991907.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991947) 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 in 5 ways as a sum of consecutive naturals, for example, 110655 + ... + 110672.

It is an arithmetic number, because the mean of its divisors is an integer number (479544).

2^1991943 is an apocalyptic number.

1991943 is a deficient number, since it is larger than the sum of its proper divisors (885321).

1991943 is a wasteful number, since it uses less digits than its factorization.

1991943 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 221333 (or 221330 counting only the distinct ones).

The product of its digits is 8748, while the sum is 36.

The square root of 1991943 is about 1411.3621080361. The cubic root of 1991943 is about 125.8226908922.

The spelling of 1991943 in words is "one million, nine hundred ninety-one thousand, nine hundred forty-three".