199111981 has 2 divisors, whose sum is σ = 199111982. Its totient is φ = 199111980.

The previous prime is 199111967. The next prime is 199111987. The reversal of 199111981 is 189111991.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 199092100 + 19881 = 14110^2 + 141^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-199111981 is a prime.

It is a super-2 number, since 2×199111981² = 79291161955488722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (199111987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 99555990 + 99555991.

It is an arithmetic number, because the mean of its divisors is an integer number (99555991).

Almost surely, 2^199111981 is an apocalyptic number.

It is an amenable number.

199111981 is a deficient number, since it is larger than the sum of its proper divisors (1).

199111981 is an equidigital number, since it uses as much as digits as its factorization.

199111981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5832, while the sum is 40.

The square root of 199111981 is about 14110.7044827677. The cubic root of 199111981 is about 583.9367356955.

The spelling of 199111981 in words is "one hundred ninety-nine million, one hundred eleven thousand, nine hundred eighty-one".