1821865 has 4 divisors (see below), whose sum is σ = 2186244. Its totient is φ = 1457488.

The previous prime is 1821857. The next prime is 1821871. The reversal of 1821865 is 5681281.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 746496 + 1075369 = 864^2 + 1037^2 .

It is a cyclic number.

It is not a de Polignac number, because 1821865 - 2³ = 1821857 is a prime.

It is a Smith number, since the sum of its digits (31) 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 an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 182182 + ... + 182191.

It is an arithmetic number, because the mean of its divisors is an integer number (546561).

2^1821865 is an apocalyptic number.

It is an amenable number.

1821865 is a deficient number, since it is larger than the sum of its proper divisors (364379).

1821865 is an equidigital number, since it uses as much as digits as its factorization.

1821865 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 364378.

The product of its digits is 3840, while the sum is 31.

The square root of 1821865 is about 1349.7647943253. The cubic root of 1821865 is about 122.1346046364.

The spelling of 1821865 in words is "one million, eight hundred twenty-one thousand, eight hundred sixty-five".