1856821121 has 2 divisors, whose sum is σ = 1856821122. Its totient is φ = 1856821120.

The previous prime is 1856821103. The next prime is 1856821123. The reversal of 1856821121 is 1211286581.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1727316721 + 129504400 = 41561^2 + 11380^2 .

It is an emirp because it is prime and its reverse (1211286581) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1856821121 - 2²⁶ = 1789712257 is a prime.

Together with 1856821123, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (1856821123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 928410560 + 928410561.

It is an arithmetic number, because the mean of its divisors is an integer number (928410561).

Almost surely, 2^1856821121 is an apocalyptic number.

It is an amenable number.

1856821121 is a deficient number, since it is larger than the sum of its proper divisors (1).

1856821121 is an equidigital number, since it uses as much as digits as its factorization.

1856821121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7680, while the sum is 35.

The square root of 1856821121 is about 43090.8472996297. The cubic root of 1856821121 is about 1229.1079351539.

The spelling of 1856821121 in words is "one billion, eight hundred fifty-six million, eight hundred twenty-one thousand, one hundred twenty-one".