1891891 has 4 divisors (see below), whose sum is σ = 1932192. Its totient is φ = 1851592.

The previous prime is 1891889. The next prime is 1891907. The reversal of 1891891 is 1981981.

It is a happy number.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1981981 = 41 ⋅48341.

It is a cyclic number.

It is not a de Polignac number, because 1891891 - 2¹ = 1891889 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1891891.

It is not an unprimeable number, because it can be changed into a prime (1891861) 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, 20080 + ... + 20173.

It is an arithmetic number, because the mean of its divisors is an integer number (483048).

2^1891891 is an apocalyptic number.

1891891 is a deficient number, since it is larger than the sum of its proper divisors (40301).

1891891 is an equidigital number, since it uses as much as digits as its factorization.

1891891 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40300.

The product of its digits is 5184, while the sum is 37.

The square root of 1891891 is about 1375.4602865950. The cubic root of 1891891 is about 123.6797799085.

It can be divided in two parts, 189 and 1891, that added together give a triangular number (2080 = T₆₄).

The spelling of 1891891 in words is "one million, eight hundred ninety-one thousand, eight hundred ninety-one".