198181861 has 2 divisors, whose sum is σ = 198181862. Its totient is φ = 198181860.

The previous prime is 198181859. The next prime is 198181873. The reversal of 198181861 is 168181891.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 195720100 + 2461761 = 13990^2 + 1569^2 .

It is a cyclic number.

It is not a de Polignac number, because 198181861 - 2¹ = 198181859 is a prime.

Together with 198181859, it forms a pair of twin primes.

198181861 is a strobogrammatic number because it is the same when read upside-down.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (198181811) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99090930 + 99090931.

It is an arithmetic number, because the mean of its divisors is an integer number (99090931).

Almost surely, 2^198181861 is an apocalyptic number.

It is an amenable number.

198181861 is a deficient number, since it is larger than the sum of its proper divisors (1).

198181861 is an equidigital number, since it uses as much as digits as its factorization.

198181861 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 27648, while the sum is 43.

The square root of 198181861 is about 14077.7079455428. The cubic root of 198181861 is about 583.0260602846.

The spelling of 198181861 in words is "one hundred ninety-eight million, one hundred eighty-one thousand, eight hundred sixty-one".