19931991 has 8 divisors (see below), whose sum is σ = 26601600. Its totient is φ = 13275192.

The previous prime is 19931987. The next prime is 19931999. The reversal of 19931991 is 19913991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 19931991 - 2² = 19931987 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19931999) 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 7 ways as a sum of consecutive naturals, for example, 1360 + ... + 6458.

It is an arithmetic number, because the mean of its divisors is an integer number (3325200).

Almost surely, 2^19931991 is an apocalyptic number.

19931991 is a deficient number, since it is larger than the sum of its proper divisors (6669609).

19931991 is a wasteful number, since it uses less digits than its factorization.

19931991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6405.

The product of its digits is 19683, while the sum is 42.

The square root of 19931991 is about 4464.5258426848. The cubic root of 19931991 is about 271.1337375422.

The spelling of 19931991 in words is "nineteen million, nine hundred thirty-one thousand, nine hundred ninety-one".