1851821 has 2 divisors, whose sum is σ = 1851822. Its totient is φ = 1851820.

The previous prime is 1851809. The next prime is 1851841. The reversal of 1851821 is 1281581.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1653796 + 198025 = 1286^2 + 445^2 .

It is a cyclic number.

It is not a de Polignac number, because 1851821 - 2⁶ = 1851757 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1851841) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 925910 + 925911.

It is an arithmetic number, because the mean of its divisors is an integer number (925911).

2^1851821 is an apocalyptic number.

It is an amenable number.

1851821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1851821 is an equidigital number, since it uses as much as digits as its factorization.

1851821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 640, while the sum is 26.

The square root of 1851821 is about 1360.8162991381. The cubic root of 1851821 is about 122.8003679957.

The spelling of 1851821 in words is "one million, eight hundred fifty-one thousand, eight hundred twenty-one".