1991543 has 4 divisors (see below), whose sum is σ = 2002728. Its totient is φ = 1980360.

The previous prime is 1991527. The next prime is 1991551. The reversal of 1991543 is 3451991.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1991543 - 2⁴ = 1991527 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1991503) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5321 + ... + 5682.

It is an arithmetic number, because the mean of its divisors is an integer number (500682).

2^1991543 is an apocalyptic number.

1991543 is a deficient number, since it is larger than the sum of its proper divisors (11185).

1991543 is a wasteful number, since it uses less digits than its factorization.

1991543 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11184.

The product of its digits is 4860, while the sum is 32.

The square root of 1991543 is about 1411.2203938436. The cubic root of 1991543 is about 125.8142682205.

The spelling of 1991543 in words is "one million, nine hundred ninety-one thousand, five hundred forty-three".