1991611 has 4 divisors (see below), whose sum is σ = 1994512. Its totient is φ = 1988712.

The previous prime is 1991609. The next prime is 1991617. The reversal of 1991611 is 1161991.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 1991611 - 2¹ = 1991609 is a prime.

It is a Duffinian number.

1991611 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 1991611.

It is not an unprimeable number, because it can be changed into a prime (1991617) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 226 + ... + 2008.

It is an arithmetic number, because the mean of its divisors is an integer number (498628).

2^1991611 is an apocalyptic number.

1991611 is a deficient number, since it is larger than the sum of its proper divisors (2901).

1991611 is a wasteful number, since it uses less digits than its factorization.

1991611 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2900.

The product of its digits is 486, while the sum is 28.

The square root of 1991611 is about 1411.2444862603. The cubic root of 1991611 is about 125.8157001543.

The spelling of 1991611 in words is "one million, nine hundred ninety-one thousand, six hundred eleven".