199871989 has 2 divisors, whose sum is σ = 199871990. Its totient is φ = 199871988.

The previous prime is 199871983. The next prime is 199871993. The reversal of 199871989 is 989178991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 119464900 + 80407089 = 10930^2 + 8967^2 .

It is an emirp because it is prime and its reverse (989178991) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 199871989 - 2¹⁷ = 199740917 is a prime.

It is a super-2 number, since 2×199871989² = 79897623973632242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199871983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99935994 + 99935995.

It is an arithmetic number, because the mean of its divisors is an integer number (99935995).

Almost surely, 2^199871989 is an apocalyptic number.

It is an amenable number.

199871989 is a deficient number, since it is larger than the sum of its proper divisors (1).

199871989 is an equidigital number, since it uses as much as digits as its factorization.

199871989 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2939328, while the sum is 61.

The square root of 199871989 is about 14137.6090269890. The cubic root of 199871989 is about 584.6787522019.

The spelling of 199871989 in words is "one hundred ninety-nine million, eight hundred seventy-one thousand, nine hundred eighty-nine".