1991427937 has 4 divisors (see below), whose sum is σ = 1992190356. Its totient is φ = 1990665520.

The previous prime is 1991427931. The next prime is 1991427959. The reversal of 1991427937 is 7397241991.

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

It can be written as a sum of positive squares in 2 ways, for example, as 1864166976 + 127260961 = 43176^2 + 11281^2 .

It is a cyclic number.

It is not a de Polignac number, because 1991427937 - 2¹⁵ = 1991395169 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991427931) 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, 377278 + ... + 382519.

It is an arithmetic number, because the mean of its divisors is an integer number (498047589).

Almost surely, 2^1991427937 is an apocalyptic number.

It is an amenable number.

1991427937 is a deficient number, since it is larger than the sum of its proper divisors (762419).

1991427937 is an equidigital number, since it uses as much as digits as its factorization.

1991427937 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 762418.

The product of its digits is 857304, while the sum is 52.

The square root of 1991427937 is about 44625.4180596664. The cubic root of 1991427937 is about 1258.1184516700.

The spelling of 1991427937 in words is "one billion, nine hundred ninety-one million, four hundred twenty-seven thousand, nine hundred thirty-seven".