1891009 has 4 divisors (see below), whose sum is σ = 1923120. Its totient is φ = 1858900.

The previous prime is 1891007. The next prime is 1891027. The reversal of 1891009 is 9001981.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 9001981 = 1933 ⋅4657.

It is a cyclic number.

It is not a de Polignac number, because 1891009 - 2¹ = 1891007 is a prime.

It is a Duffinian number.

1891009 is a lucky number.

It is not an unprimeable number, because it can be changed into a prime (1891007) 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, 15967 + ... + 16084.

It is an arithmetic number, because the mean of its divisors is an integer number (480780).

2^1891009 is an apocalyptic number.

It is an amenable number.

1891009 is a deficient number, since it is larger than the sum of its proper divisors (32111).

1891009 is an equidigital number, since it uses as much as digits as its factorization.

1891009 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32110.

The product of its (nonzero) digits is 648, while the sum is 28.

The square root of 1891009 is about 1375.1396292741. The cubic root of 1891009 is about 123.6605570741.

Subtracting from 1891009 its sum of digits (28), we obtain a palindrome (1890981).

The spelling of 1891009 in words is "one million, eight hundred ninety-one thousand, nine".