1803821 has 4 divisors (see below), whose sum is σ = 1882272. Its totient is φ = 1725372.

The previous prime is 1803817. The next prime is 1803863. The reversal of 1803821 is 1283081.

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: 1283081 = 127 ⋅10103.

It is a cyclic number.

It is not a de Polignac number, because 1803821 - 2² = 1803817 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23), and also a Moran number because the ratio is a prime number: 78427 = 1803821 / (1 + 8 + 0 + 3 + 8 + 2 + 1).

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1803811) 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, 39191 + ... + 39236.

It is an arithmetic number, because the mean of its divisors is an integer number (470568).

2^1803821 is an apocalyptic number.

It is an amenable number.

1803821 is a deficient number, since it is larger than the sum of its proper divisors (78451).

1803821 is an equidigital number, since it uses as much as digits as its factorization.

1803821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78450.

The product of its (nonzero) digits is 384, while the sum is 23.

The square root of 1803821 is about 1343.0640342143. The cubic root of 1803821 is about 121.7300534991.

The spelling of 1803821 in words is "one million, eight hundred three thousand, eight hundred twenty-one".