1991091 has 8 divisors (see below), whose sum is σ = 2811024. Its totient is φ = 1249280.

The previous prime is 1991089. The next prime is 1991107. The reversal of 1991091 is 1901991.

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

It is a cyclic number.

It is not a de Polignac number, because 1991091 - 2¹ = 1991089 is a prime.

It is not an unprimeable number, because it can be changed into a prime (1991071) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 19470 + ... + 19571.

It is an arithmetic number, because the mean of its divisors is an integer number (351378).

2^1991091 is an apocalyptic number.

1991091 is a deficient number, since it is larger than the sum of its proper divisors (819933).

1991091 is a wasteful number, since it uses less digits than its factorization.

1991091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39061.

The product of its (nonzero) digits is 729, while the sum is 30.

The square root of 1991091 is about 1411.0602396780. The cubic root of 1991091 is about 125.8047492442.

The spelling of 1991091 in words is "one million, nine hundred ninety-one thousand, ninety-one".