1821091 has 4 divisors (see below), whose sum is σ = 1928232. Its totient is φ = 1713952.

The previous prime is 1821067. The next prime is 1821101. The reversal of 1821091 is 1901281.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1901281 = 83 ⋅22907.

It is a cyclic number.

It is not a de Polignac number, because 1821091 - 2⁹ = 1820579 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1821191) 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, 53545 + ... + 53578.

It is an arithmetic number, because the mean of its divisors is an integer number (482058).

2^1821091 is an apocalyptic number.

1821091 is a deficient number, since it is larger than the sum of its proper divisors (107141).

1821091 is a wasteful number, since it uses less digits than its factorization.

1821091 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107140.

The product of its (nonzero) digits is 144, while the sum is 22.

The square root of 1821091 is about 1349.4780472464. The cubic root of 1821091 is about 122.1173063232.

It can be divided in two parts, 18210 and 91, that multiplied together give a triangular number (1657110 = T₁₈₂₀).

The spelling of 1821091 in words is "one million, eight hundred twenty-one thousand, ninety-one".