1851836565221 has 2 divisors, whose sum is σ = 1851836565222. Its totient is φ = 1851836565220.

The previous prime is 1851836565191. The next prime is 1851836565247. The reversal of 1851836565221 is 1225656381581.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1127814264196 + 724022301025 = 1061986^2 + 850895^2 .

It is a cyclic number.

It is not a de Polignac number, because 1851836565221 - 2¹⁰ = 1851836564197 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1851836765221) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 925918282610 + 925918282611.

It is an arithmetic number, because the mean of its divisors is an integer number (925918282611).

Almost surely, 2^{1851836565221} is an apocalyptic number.

It is an amenable number.

1851836565221 is a deficient number, since it is larger than the sum of its proper divisors (1).

1851836565221 is an equidigital number, since it uses as much as digits as its factorization.

1851836565221 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3456000, while the sum is 53.

The spelling of 1851836565221 in words is "one trillion, eight hundred fifty-one billion, eight hundred thirty-six million, five hundred sixty-five thousand, two hundred twenty-one".