19991943 has 12 divisors (see below), whose sum is σ = 28917720. Its totient is φ = 13309296.

The previous prime is 19991911. The next prime is 19991963. The reversal of 19991943 is 34919991.

It is not a de Polignac number, because 19991943 - 2⁵ = 19991911 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19991963) 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 11 ways as a sum of consecutive naturals, for example, 8980 + ... + 10982.

It is an arithmetic number, because the mean of its divisors is an integer number (2409810).

Almost surely, 2^19991943 is an apocalyptic number.

19991943 is a deficient number, since it is larger than the sum of its proper divisors (8925777).

19991943 is a wasteful number, since it uses less digits than its factorization.

19991943 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3118 (or 3115 counting only the distinct ones).

The product of its digits is 78732, while the sum is 45.

The square root of 19991943 is about 4471.2350642747. The cubic root of 19991943 is about 271.4053066592.

The spelling of 19991943 in words is "nineteen million, nine hundred ninety-one thousand, nine hundred forty-three".