1911891 has 4 divisors (see below), whose sum is σ = 2549192. Its totient is φ = 1274592.

The previous prime is 1911887. The next prime is 1911893. The reversal of 1911891 is 1981191.

It is a happy number.

1911891 is an esthetic number in base 3, because in such base its adjacent digits differ by 1.

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

It is not a de Polignac number, because 1911891 - 2² = 1911887 is a prime.

It is a D-number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1911893) 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, 318646 + ... + 318651.

It is an arithmetic number, because the mean of its divisors is an integer number (637298).

2^1911891 is an apocalyptic number.

1911891 is a deficient number, since it is larger than the sum of its proper divisors (637301).

1911891 is an equidigital number, since it uses as much as digits as its factorization.

1911891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 637300.

The product of its digits is 648, while the sum is 30.

The square root of 1911891 is about 1382.7114666480. The cubic root of 1911891 is about 124.1140772946.

The spelling of 1911891 in words is "one million, nine hundred eleven thousand, eight hundred ninety-one".