1818161861 has 2 divisors, whose sum is σ = 1818161862. Its totient is φ = 1818161860.

The previous prime is 1818161809. The next prime is 1818161881. The reversal of 1818161861 is 1681618181.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1716030625 + 102131236 = 41425^2 + 10106^2 .

It is an emirp because it is prime and its reverse (1681618181) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 1981918181 and 1818191891.

It is a cyclic number.

It is not a de Polignac number, because 1818161861 - 2¹⁰ = 1818160837 is a prime.

It is a Sophie Germain 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 (1818161801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 909080930 + 909080931.

It is an arithmetic number, because the mean of its divisors is an integer number (909080931).

Almost surely, 2^1818161861 is an apocalyptic number.

It is an amenable number.

1818161861 is a deficient number, since it is larger than the sum of its proper divisors (1).

1818161861 is an equidigital number, since it uses as much as digits as its factorization.

1818161861 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18432, while the sum is 41.

The square root of 1818161861 is about 42639.9092517796. The cubic root of 1818161861 is about 1220.5179787861.

The spelling of 1818161861 in words is "one billion, eight hundred eighteen million, one hundred sixty-one thousand, eight hundred sixty-one".