1991579 has 4 divisors (see below), whose sum is σ = 1999200. Its totient is φ = 1983960.

The previous prime is 1991573. The next prime is 1991597. The reversal of 1991579 is 9751991.

It is a happy number.

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 1991579 - 2¹² = 1987483 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991573) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3404 + ... + 3945.

It is an arithmetic number, because the mean of its divisors is an integer number (499800).

2^1991579 is an apocalyptic number.

1991579 is a deficient number, since it is larger than the sum of its proper divisors (7621).

1991579 is an equidigital number, since it uses as much as digits as its factorization.

1991579 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7620.

The product of its digits is 25515, while the sum is 41.

The square root of 1991579 is about 1411.2331487036. The cubic root of 1991579 is about 125.8150263072.

The spelling of 1991579 in words is "one million, nine hundred ninety-one thousand, five hundred seventy-nine".