1820921 has 16 divisors (see below), whose sum is σ = 2052864. Its totient is φ = 1607424.

The previous prime is 1820899. The next prime is 1820927. The reversal of 1820921 is 1290281.

1820921 is nontrivially palindromic in base 4.

It is a cyclic number.

It is not a de Polignac number, because 1820921 - 2⁶ = 1820857 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1820927) 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 15 ways as a sum of consecutive naturals, for example, 34331 + ... + 34383.

It is an arithmetic number, because the mean of its divisors is an integer number (128304).

2^1820921 is an apocalyptic number.

It is an amenable number.

1820921 is a deficient number, since it is larger than the sum of its proper divisors (231943).

1820921 is a wasteful number, since it uses less digits than its factorization.

1820921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 160.

The product of its (nonzero) digits is 288, while the sum is 23.

The square root of 1820921 is about 1349.4150584605. The cubic root of 1820921 is about 122.1135062956.

The spelling of 1820921 in words is "one million, eight hundred twenty thousand, nine hundred twenty-one".