1991011 has 4 divisors (see below), whose sum is σ = 2172024. Its totient is φ = 1810000.

The previous prime is 1990987. The next prime is 1991027. The reversal of 1991011 is 1101991.

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 1991011 - 2⁷ = 1990883 is a prime.

It is a pancake number, because a pancake can be divided into 1991011 parts by 1995 straight cuts.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1991071) 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 3 ways as a sum of consecutive naturals, for example, 90490 + ... + 90511.

It is an arithmetic number, because the mean of its divisors is an integer number (543006).

2^1991011 is an apocalyptic number.

1991011 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

1991011 is a deficient number, since it is larger than the sum of its proper divisors (181013).

1991011 is a wasteful number, since it uses less digits than its factorization.

1991011 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 181012.

The product of its (nonzero) digits is 81, while the sum is 22.

The square root of 1991011 is about 1411.0318919146. The cubic root of 1991011 is about 125.8030643196.

The spelling of 1991011 in words is "one million, nine hundred ninety-one thousand, eleven".