1856821 has 2 divisors, whose sum is σ = 1856822. Its totient is φ = 1856820.

The previous prime is 1856819. The next prime is 1856837. The reversal of 1856821 is 1286581.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1664100 + 192721 = 1290^2 + 439^2 .

It is an emirp because it is prime and its reverse (1286581) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1856821 - 2¹ = 1856819 is a prime.

Together with 1856819, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1856801) 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 as a sum of consecutive naturals, namely, 928410 + 928411.

It is an arithmetic number, because the mean of its divisors is an integer number (928411).

2^1856821 is an apocalyptic number.

It is an amenable number.

1856821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1856821 is an equidigital number, since it uses as much as digits as its factorization.

1856821 is an odious number, because the sum of its binary digits is odd.

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

The square root of 1856821 is about 1362.6521933347. The cubic root of 1856821 is about 122.9107908456.

The spelling of 1856821 in words is "one million, eight hundred fifty-six thousand, eight hundred twenty-one".