1811221 has 4 divisors (see below), whose sum is σ = 1814092. Its totient is φ = 1808352.

The previous prime is 1811219. The next prime is 1811287. The reversal of 1811221 is 1221181.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1221181 = 13 ⋅93937.

It can be written as a sum of positive squares in 2 ways, for example, as 579121 + 1232100 = 761^2 + 1110^2 .

It is a cyclic number.

It is not a de Polignac number, because 1811221 - 2¹ = 1811219 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1811195 and 1811204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1811291) 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, 30 + ... + 1903.

It is an arithmetic number, because the mean of its divisors is an integer number (453523).

2^1811221 is an apocalyptic number.

It is an amenable number.

1811221 is a deficient number, since it is larger than the sum of its proper divisors (2871).

1811221 is an equidigital number, since it uses as much as digits as its factorization.

1811221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2870.

The product of its digits is 32, while the sum is 16.

The square root of 1811221 is about 1345.8161092809. The cubic root of 1811221 is about 121.8962882822.

The spelling of 1811221 in words is "one million, eight hundred eleven thousand, two hundred twenty-one".