1991583791 has 4 divisors (see below), whose sum is σ = 2001903072. Its totient is φ = 1981264512.

The previous prime is 1991583773. The next prime is 1991583821. The reversal of 1991583791 is 1973851991.

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 1991583791 - 2¹⁰ = 1991582767 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 (1991583691) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5159351 + ... + 5159736.

It is an arithmetic number, because the mean of its divisors is an integer number (500475768).

Almost surely, 2^1991583791 is an apocalyptic number.

1991583791 is a deficient number, since it is larger than the sum of its proper divisors (10319281).

1991583791 is a wasteful number, since it uses less digits than its factorization.

1991583791 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10319280.

The product of its digits is 612360, while the sum is 53.

The square root of 1991583791 is about 44627.1642724473. The cubic root of 1991583791 is about 1258.1512719518.

The spelling of 1991583791 in words is "one billion, nine hundred ninety-one million, five hundred eighty-three thousand, seven hundred ninety-one".