1851808121 has 2 divisors, whose sum is σ = 1851808122. Its totient is φ = 1851808120.

The previous prime is 1851808099. The next prime is 1851808129. The reversal of 1851808121 is 1218081581.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1143183721 + 708624400 = 33811^2 + 26620^2 .

It is an emirp because it is prime and its reverse (1218081581) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1851808121 is a prime.

It is not a weakly prime, because it can be changed into another prime (1851808129) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 925904060 + 925904061.

It is an arithmetic number, because the mean of its divisors is an integer number (925904061).

Almost surely, 2^1851808121 is an apocalyptic number.

It is an amenable number.

1851808121 is a deficient number, since it is larger than the sum of its proper divisors (1).

1851808121 is an equidigital number, since it uses as much as digits as its factorization.

1851808121 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5120, while the sum is 35.

The square root of 1851808121 is about 43032.6401816110. The cubic root of 1851808121 is about 1228.0008331206. Note that the first 3 decimals are identical.

The spelling of 1851808121 in words is "one billion, eight hundred fifty-one million, eight hundred eight thousand, one hundred twenty-one".